Yaya was actually very helpful. She replied within 2 days apologizing, saying she would not endorse a product that was not being delivered, and saying she had emailed Carlos and advised him to refund my money.
Around the same time, a very kind member of this forum directed my post to the person who runs Florida Super Con 2013 (where Carlos Blanchard is the cosplay director). It is my understanding that the Super Con bigwig said he'd talk to Carlos about this issue.
After those two things happened, Carlos finally posted on his FB timeline apologizing. Still no refund. Still no corset. Still no response other than that FB post, in which Carlos asked that his customers refrain from contacting anyone not involved with the situation, since Carlos is "solely responsible."
There's a bit more to the story, but I don't want to ramble too long. My lawyer, who also happens to be my dad, has gotten involved now and I don't know what's going to happen. I do know, this being my first time actually commissioning an item rather than making it myself, that I will be steering clear of the process in the future. I'd rather have a half-ass item I made myself than go through all this again.