With no texts, no calls, no contact, no support when you're down, and the guy isn't even around, you don't have a relationship.
You have a pen pal who has stopped contacting you.
He has his chance. He blew it.
Time to move on.
PS If you think his depression was severe enough that he could have been considering suicide, then I suggest you contact a mutual friend to at least assure the guy is okay. But afterwards, my advice still stands. There is nothing there to hold onto, sorry.