Wow, this is pretty low and it sucks horribly.
I think eddie0776 has a good point. It seems there's more to this than is being presented.
Also, according to the tracking information, a notice was left the day before he went to pick it up at the post office. Not that it really matters.
In any event, there is always small claims court. You know the person has the merchandise. He picked it up at the post office, and signed for it. Legally, the person that bought the cue is due a cue from you or a refund, so you need to make that right (it sounds like you are making another for him). You might try to contact the police, but if that fails you can still sue him in small claims court and get a judgement against him. Whether or not he follows through after the judgement is another issue, and you need to find ways to obtain the judgement. At the very least you will have a legal basis after the judgement.
If there was bad blood, perhaps it's time to bury the hatchet and offer that cue as a peace offering to settle matters. Escalating it will cost time and money from both parties. If that Barry person truly is a d-bag, and doing it out of selfishness, then stick it to him as best you can.
Good luck, and I hope this situation resolves itself after some level headed talks.