I had the exact same thing happen to me with my Ford F-150, butI was luckier then you.
I had just returned from a 1200 mile trip from the Florida Keys, and tried to back into my drive way, only to find out I had no reverse. Luckily my neighbor didn't mind me pulling into her pasture, unhitching, and then I drove it to my local garage.
I think what killed mine was the steep mountains that I have to go over to get home, ( I am not sure why that caused the reverse to go out, but it sure puts a strain on the transmission)
Jack L