Op...two things seem clear to me.
1 - The fact that you are so worried and intimidated and still considering your options means you have lost. You don't seem like you are going to do what you should do...tell the guy to pay up or take a hike. That is as simple as it is. You bought it, you own it. If it was his, he should have had possession of it. Stop fretting about it, and man up.
and 2: It strikes me as a fairly good scam to run. Get the "wife" to sell a pin, then the fake ex-husband tracks the buyer down and demands the pin back. If you are forceful enough and know the game, you can probably get to keep the pin and the money a decent percentage of the time.

Anyhoo.....

Chaos