Sorry for your loss, shasan. I've tagged the user, lets see if he responds.
Some strange things have gone on with that account lately. Looks like it may have been hacked and then recovered. And I found this topic about the user:
https://bitcointalk.org/index.php?topic=5111751.0Could also be due to account being sold and then recovered illegitimately. Who knows.
But these should have all been red flags. I personally would not have been comfortable with dealing with this guy even with a signed message, because of all the shady activity that has gone on in regards to password changes and account recoveries.
Besides, all of his trust was given prior to his account being recovered, which means that they should have been discounted in my opinion.
Anyways, this is a risk of a no collateral loan that everyone knows about, and I think shasan was prepared to take it. I highly doubt that the guy is coming back given that it's been a month since the due date.