Without giving too many details, I've had a first for a commission: My commissioner has vanished, but the commission is fully paid and mostly completed. I don't have any other method of contact, other than their email and FA account.

I last sent a request for the remaining reference information for the last, extra versions on Feb 16, 2018, but the first versions were sent just after midnight on Feb 15. The customer last added something to their FA account on March 6, 2018. I have 2 versions to complete, a NSFW and a clothed version (the character is "Ken doll" nude before they started molding the underwear on right now). These refs were originally requested on February 8, after the commission was confirmed.

One of the versions was included in the sale price, the other was an add-on fee.

At this point, I'm not 100% sure what to do? I can't complete the other versions without the references, and the commissioner has the completed part as is. Should I refund them partially (for the work not completed) and say "Hey, I can complete this when you have the other refs, just shoot me an email!" or continue sitting on it?