Glad to see the OP ask this question rather than just selling their stuff and leaving their thread open.
Perhaps there should be a sticky explaining how to close a Classifieds thread.
Thread-closing within 24 hours of receiving funds should be mandatory and violators (with no valid reason beyond "oops, my bad") should lose all Classified privileges for a long, long, time. This would very likely turn habitual offenders into one-timers.
The "I use Tapatalk so I can't close it" excuse is getting old. If a user cannot close a thread through Tapatalk then they shouldn't be able to open one through Tapatalk. Simple as that.
Several times recently I've been on the fence about a sale (do I really need four more tanks or another VF) and after watching a week or more of no bites figured what the heck, I'll help a vaper out and take them off their hands, only to get a message back saying they sold them days ago.
Kind of brings up another sore spot for me: users (buyers AND sellers) who ignore the thread and communicate strictly with PMs/conversations. I know the "rules" don't require thread communication beyond closing it (which is often ignored) but the absence of a rule doesn't justify an absence of courtesy.