I'd just tell the buyer the deal is off and resell the cards. No need for feedback at all. Sure it's frustrating, but it happens. If you do ever receive a check, just shred it. Don't really know how this went on for 16 days, but I would have told him the deal is off after a couple days. I used to wait for payments for a couple of days fairly often, but not much any more, to many deals go south that way.
Check out my photobucket by clicking on my homepage in the drop down list under my username. Looking for any Twins cards I don't have, and Mickey Mantle refractors that I don't have. I will trade for bait, on occasion. 2011 Topps Chrome auto set completed!!