So when C9 was still up, I was doing business w/someone by the username of DankExpress who I'd like to get a hold of again if I could. He had sent me some contact information that then got lost due to the market going down. Does anyone know if he's operating on any of the other markets/if I would be able to get my messages from C9 (I'm assuming the answer to the last one is "no" but it never hurts to ask)
You can use Grams to search. Or if you have his public key he may have put his email address in there. These addresses are often only checked when the market goes down so your mileage may vary.