I Have No Mouth - GOG version (OSX)
Played on ScummVM 1.8.0git2784-g2fa47e2 (Feb 25 2015 05:01:51) on OSX 10.9.5
When playing Nimdok, in the oven cave behind the vent, there is a gold watch and a pair of pliers on the table. If you take those items, leave the room through the iron door and then return to the room via the vent, the items can still be looked at in their previous spot on the table even though their sprites are not visible. The items can be taken again but do not show up twice in your inventory.
I've just confirmed that this bug also appears when running the game under DosBox. I guess this is a game bug and not a ScummVM bug. Feel free to close this issue if you think it's appropriate.