As much as I don't want to go this route, tomorrow I will mail buyer a USPS Certified Letter with return receipt. This is at my expense and I'm not to happy about doing this. I will be nice in my letter, but firm.
does his forum name contain the letters CZ?
Some good advice. I would send certified letter, email, phone call telling him his check has cleared (if it has) and that you want the firearm picked up. I'd give him a very specific time by which to contact you (say a month). At that point if you haven't been contacted, you will put the firearm backup for sale and will send him a refund once you resell it.
What's the hurry?
I don't see giving it to the state as the high road, more like a different road to take if so inclined.In Michigan, a company that can't connect with someone they owe money to, sends the money with a description of who belongs to it to the state. The one that it belongs to can claim the money from the state and the company can legally clear their books of the transaction.
Look to see if there is something like that in your state and take the high road. Then you can re-list the firearm with a clear conscious.
Clutch
I hate to say it, but he is likely dead.