Never misplaced a thing in any MM game - though I tend to forget where I put things, as I generally store too much as the game progresses.

The Temple of the Sun is btw. a good place, if not the best, to store lots of stuff and to place a beacon for Bootleg Bay area. Likewise is Clanker's Laboratory in MM7 a good storing place - even better than Castle Harmondale, I think. In MM8 you have plenty of storage, the more members you gather in the Adventurer's Inn the better - you even get "dolls" for your unused artefacts.