I have sold and bought a lot of things from the "buy and sell" forum, and found that it is best not to mark anything sold until the cash is in hand.
I once put a fish up for sale, and the potential buyer sent me a PM saying he was coming to pick it up. Another potential buyer sent a PM 15 minutes after the first saying he could come at 8:30 PM to pick it up.
When I told the second buyer he should pick it up right away as there was another buyer he became angry and said I should not do that because it was not ethical.
The outcome of the story is that the fish is still here because the first buyer did not show. The second buyer won't talk to me any more.
All this because something was considered "sold" before the money was in hand.
