Excellent point.
So fantasy piece is still high on the probability list.
But, I have seen a fair number of "Mick gave me this jersey" (I actually have a Joe DiMaggio one); so that is probably my last thought.
Really, unless I find a photo, or produce a reliable witness, this is just all fun and games.
However, I am pretty sure it really was worn by Fisher, and likely by "Hop" Cassady (Thanks Brandon554!). That means it very likely did get washed with Mick's jersey!