I can see that argument (from joefarebrother).
OTOH, it could also be that due to Donate, at end of turn you trash a card, you gain a Gold with Market Square and play Sheepdog using Way of the Mouse, playing a Black Market, playing Scepter and finally replaying the Gear or Secret Cave that you didn't make stay out on the first play.
So after thinking about it some more, the sensible solution to me (right now
) would be to have a Duration card check at Clean-up
1) is there an effect from it after this turn at all,
2) if yes, will any of these effects accomplish anything?
If one of the future effects will accomplish anything (given current data), the Duration card stays out, otherwise not (or better, this particular test if the card stays out says "not because of me").
For Gear. 1) would be true always (unless it was played using a Way or under Enchantress). But if no cards were set aside, check 2 would fail.
The same argument should apply IMO to Garrison and Cargo Ship, if no relevant cards were gained.
And while this does open the possibility that a card is gained later (with it being set aside on "nothing" for Cargo Ship), this is a rare occurance that should not make the general decision more complicated. And it's also something that is already possible using Throne Room - like cards and Way of the Horse/Butterfly.