Basically, I had a deal lined up and the buyer sent the gold first. I returned the gold and then sent the item with a 100k CoD attached, for both our safety (ironically). He sent me a message saying "ty for the deal!". So, I check my mail, no gold. Re-log, still no gold. I talked with the buyer and he has the item and it took 100k gold from him, but ZOS' servers never relayed it back to me.
I've put a ticket in, as did the buyer. I've done hundreds of CoD deals and this has never happened.
I would highly advise people to avoid CoD exchanges and trade directly.
I'll update if/when this is resolved.