Just had something REALLY REALLY weird happen in my game.
I deleted one of the IFs because he was annoying, mean spirited and such.
I reloaded the file sometime later [Or reset objects via MC, not sure]. The IF reappeared in my sim's pocket, sometime after she turned into a teen.
I thought nothing of it until I got a message that he wanted to come out... and I let him out... and he aged up and acted like nothing happened!