While I've been playing here, I've noticed that if I don't mem detect magic before I rent, it will be removed from the "to mem" list when I unrent. I recently asked Oteb if this happened to him. He said yes, and that it also happens to him with the gate spell. I decided to run a test to see which spells this happens to. The results are shown below. I think I was talking to Malia also, and he said that all caster classes are affected. The test I ran shows that Invokers have 9 spells that are lost if they aren't memmed before renting.

( 1st) detect magic
( 1st) magic missile
( 4th) minor paralysis
( 4th) dispel magic
( 4th) farsee
( 5th) slowness
( 8th) major paralysis
( 9th) fell frost
( 9th) gate


 
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Before renting:
You are currently memorizing the following spells:
    3 seconds:  ( 1st) detect invisibility
    7 seconds:  ( 1st) detect magic
   10 seconds:  ( 1st) magic missile
   14 seconds:  ( 1st) burning hands
   17 seconds:  ( 1st) chill touch
   22 seconds:  ( 2nd) shocking grasp
   28 seconds:  ( 2nd) acid blast
   33 seconds:  ( 2nd) minor creation
   38 seconds:  ( 2nd) faerie fire
   44 seconds:  ( 3rd) locate object
   51 seconds:  ( 3rd) lightning bolt
   57 seconds:  ( 3rd) invisibility
   63 seconds:  ( 3rd) minute meteors
   71 seconds:  ( 5th) infravision
   79 seconds:  ( 4th) teleport
   86 seconds:  ( 4th) fireball
   93 seconds:  ( 4th) minor paralysis
  100 seconds:  ( 4th) ray of enfeeblement
  108 seconds:  ( 4th) levitate
  115 seconds:  ( 4th) dispel magic
  122 seconds:  ( 4th) mordenkainens sword
  129 seconds:  ( 4th) farsee
  138 seconds:  ( 5th) cone of cold
  146 seconds:  ( 5th) dimension door
  154 seconds:  ( 5th) fireshield
  162 seconds:  ( 5th) ice storm
  171 seconds:  ( 5th) coldshield
  179 seconds:  ( 5th) slowness
  188 seconds:  ( 6th) chain lightning
  197 seconds:  ( 6th) blazing beam
  206 seconds:  ( 6th) clairvoyance
  216 seconds:  ( 7th) bigbys clenched fist
  225 seconds:  ( 7th) incendiary cloud
  235 seconds:  ( 7th) power word stun
  248 seconds:  ( 8th) major paralysis
  260 seconds:  ( 8th) power word kill
  273 seconds:  ( 8th) thunderblast
  285 seconds:  ( 8th) disintegrate
  298 seconds:  ( 8th) force missiles
  311 seconds:  ( 9th) fell frost
  324 seconds:  ( 9th) gate
  337 seconds:  ( 9th) relocate
  340 seconds:  ( 1st) mage flame

You can memorize 5 1st, 6 2nd, 5 3rd, 3 6th, 3 7th, and 1 9th circle spell(s).

After renting:
You are currently memorizing the following spells:
    3 seconds:  ( 1st) detect invisibility
    7 seconds:  ( 1st) burning hands
   10 seconds:  ( 1st) chill touch
   15 seconds:  ( 2nd) shocking grasp
   21 seconds:  ( 2nd) acid blast
   26 seconds:  ( 2nd) minor creation
   31 seconds:  ( 2nd) faerie fire
   37 seconds:  ( 3rd) locate object
   44 seconds:  ( 3rd) lightning bolt
   50 seconds:  ( 3rd) invisibility
   56 seconds:  ( 3rd) minute meteors
   64 seconds:  ( 5th) infravision
   72 seconds:  ( 4th) teleport
   79 seconds:  ( 4th) fireball
   86 seconds:  ( 4th) ray of enfeeblement
   93 seconds:  ( 4th) levitate
  101 seconds:  ( 4th) mordenkainens sword
  109 seconds:  ( 5th) cone of cold
  117 seconds:  ( 5th) dimension door
  125 seconds:  ( 5th) fireshield
  134 seconds:  ( 5th) ice storm
  142 seconds:  ( 5th) coldshield
  151 seconds:  ( 6th) chain lightning
  160 seconds:  ( 6th) blazing beam
  169 seconds:  ( 6th) clairvoyance
  179 seconds:  ( 7th) bigbys clenched fist
  188 seconds:  ( 7th) incendiary cloud
  198 seconds:  ( 7th) power word stun
  211 seconds:  ( 8th) power word kill
  223 seconds:  ( 8th) thunderblast
  236 seconds:  ( 8th) disintegrate
  248 seconds:  ( 8th) force missiles
  261 seconds:  ( 9th) relocate
  265 seconds:  ( 1st) mage flame

You can memorize 7 1st, 6 2nd, 5 3rd, 3 4th, 1 5th, 3 6th, 3 7th, 1 8th, and 3 9
th circle spell(s).

rented/unrented, no change

forgot everything, memmed exclusively problem spells:

   13 seconds:  ( 9th) fell frost
   26 seconds:  ( 9th) gate
   29 seconds:  ( 1st) detect magic
   33 seconds:  ( 1st) magic missile
   36 seconds:  ( 1st) chill touch
   43 seconds:  ( 4th) minor paralysis
   51 seconds:  ( 4th) dispel magic
   58 seconds:  ( 4th) farsee
   66 seconds:  ( 5th) slowness
   79 seconds:  ( 8th) major paralysis
   92 seconds:  ( 9th) fell frost
  105 seconds:  ( 9th) gate
  108 seconds:  ( 1st) detect magic
  112 seconds:  ( 1st) magic missile
  115 seconds:  ( 1st) chill touch
  122 seconds:  ( 4th) minor paralysis
  130 seconds:  ( 4th) dispel magic
  137 seconds:  ( 4th) farsee
  145 seconds:  ( 5th) slowness
  158 seconds:  ( 8th) major paralysis
  161 seconds:  ( 1st) detect magic
  165 seconds:  ( 1st) magic missile
  168 seconds:  ( 1st) chill touch
  175 seconds:  ( 4th) minor paralysis
  183 seconds:  ( 4th) dispel magic
  191 seconds:  ( 5th) slowness
  203 seconds:  ( 8th) major paralysis
  207 seconds:  ( 1st) detect magic
  210 seconds:  ( 1st) magic missile
  219 seconds:  ( 5th) slowness
  231 seconds:  ( 8th) major paralysis
  239 seconds:  ( 5th) slowness
  252 seconds:  ( 8th) major paralysis
  260 seconds:  ( 5th) slowness
  268 seconds:  ( 5th) slowness

You can memorize 10 2nd, 9 3rd, 6 6th, and 6 7th circle spell(s).

rented/unrented:

You are currently memorizing the following spells:
    3 seconds:  ( 1st) chill touch
    7 seconds:  ( 1st) chill touch
   10 seconds:  ( 1st) chill touch

You can memorize 8 1st, 10 2nd, 9 3rd, 8 4th, 7 5th, 6 6th, 6 7th, 5 8th, and 4
9th circle spell(s).

forgot all, remem:

   13 seconds:  ( 9th) fell frost
   26 seconds:  ( 9th) fell frost
   39 seconds:  ( 9th) gate
   52 seconds:  ( 9th) gate
   64 seconds:  ( 8th) major paralysis
   77 seconds:  ( 8th) major paralysis
   89 seconds:  ( 8th) major paralysis
  102 seconds:  ( 8th) major paralysis
  114 seconds:  ( 8th) major paralysis
  118 seconds:  ( 1st) detect magic
  121 seconds:  ( 1st) detect magic
  125 seconds:  ( 1st) detect magic
  128 seconds:  ( 1st) detect magic
  132 seconds:  ( 1st) detect magic
  135 seconds:  ( 1st) magic missile
  139 seconds:  ( 1st) magic missile
  142 seconds:  ( 1st) magic missile
  146 seconds:  ( 1st) magic missile
  149 seconds:  ( 1st) magic missile
  153 seconds:  ( 1st) magic missile
  160 seconds:  ( 4th) minor paralysis
  167 seconds:  ( 4th) minor paralysis
  174 seconds:  ( 4th) minor paralysis
  182 seconds:  ( 4th) dispel magic
  189 seconds:  ( 4th) dispel magic
  196 seconds:  ( 4th) dispel magic
  203 seconds:  ( 4th) farsee
  211 seconds:  ( 4th) farsee
  219 seconds:  ( 5th) slowness
  227 seconds:  ( 5th) slowness
  235 seconds:  ( 5th) slowness
  244 seconds:  ( 5th) slowness
  252 seconds:  ( 5th) slowness
  260 seconds:  ( 5th) slowness
  268 seconds:  ( 5th) slowness

You can memorize 10 2nd, 9 3rd, 6 6th, and 6 7th circle spell(s).

mem:
You can memorize 11 1st, 10 2nd, 9 3rd, 8 4th, 7 5th, 6 6th, 6 7th, 5 8th, and 4
 9th circle spell(s).

conclusion:
The following invoker spells are magically lost if you 
do not mem them before renting:
    7 seconds:  ( 1st) detect magic
   10 seconds:  ( 1st) magic missile
   93 seconds:  ( 4th) minor paralysis
  115 seconds:  ( 4th) dispel magic
  129 seconds:  ( 4th) farsee
  179 seconds:  ( 5th) slowness
  248 seconds:  ( 8th) major paralysis
  311 seconds:  ( 9th) fell frost
  324 seconds:  ( 9th) gate

I tested inferno, sandblast and meteorswarm later, and they were not lost.
The Library
[Yarash's image]

[Yarash's image]