So it appears the certified letter I sent to
HashFast Technologies LLC (HashFast)
100 Bush Street, Suite 650
San Francisco, California 94104, United States
Has failed:
Your item was undeliverable as addressed at 11:49 am on January 8, 2014 in SAN FRANCISCO, CA 94104. It is being returned if appropriate information is available.
The San Jose one is still in route, but I had lower expectations of that one being successful.
Time for a process server I guess.
Son of a bitch, and I just mailed them another refund request form (and supporting documents) to that address just yesterday. Previous to that I sent it to their San Francisco address (address on my original invoice) but like you I don't have much hope of that one actually making it into their hands.