It happens in, among others, Susan Cooper's Dark is Rising sequence, so you're quite right. It's something I always *hated* about fantasy when I was young - and indeed still do. If it was me, I'd rather remember forever (with whatever attendant pain that might involve) than have something like that just taken away from me.

And I'm sorry you lost your souvenirs. *half-smile*

Interestingly it doesn't happen in the Narnia books, IIRC - at least in Lion, Witch & Wardrobe the Professor turns out to remember his own trip to Narnia very clearly..

But by the Last Battle Susan thinks it was all lets-pretend.

And there is a tendancy in Narnia for Aslan to turn round and say "Aha! You're not getting back this way", even though they worlds arn't sealed apart. In fact, given that Narnia is utterly destroyed in the last book, that's a pretty drastic perminently sealing apart, in at least some ways.