I've seen clothes get left behind, but never in a pile in a workshop, and never by non-wrestlers.
But I can accept random stuff happening.
The real problem is that it's a magma forge, and I tore down the old one to install a masterwork steel anvil in place of the iron one - but all the clothes are "owned" - by 5 different dwarfs, and aren't being dumped, and seem to be a deal-breaker for building. "Cannot reach site", which usually means there's something tasked or forbidden in the location - nope, just the clothes.
None of 5 owners (1 piece each) are smiths or furnace operators, and the forge is about 30 tiles, several halls and a variety of level changes from the barracks. No clothes anywhere else.
What's more, 2 of them have never been recruited to do any sparring - not even dabbling, nada.
The location for the forge would be a pain to duplicate - it's in its own free-standing walled enclosure, with access to magma, nicely surrounded by 8 magma furnaces - not like any 3x3 space will do.
I've tried to dump the items - nuthin'. I've tried forbidding/unforbidding, in case someone is on their way to pick one up - nope, and none of the shoeless ever comes near. I'm guessing next on the list is try to lock the owners in and manipulate their armor status? Any other suggestions?
Anyone shed any light on what's going on? Or is it just one of the mysteries of DF?