Do u think those 3 people from alcatraz who escaped survived..?

those 3 ppl that made a rubber raft and escaped, do u think they survived? many people say they didn't but, I'm wondering if they did? Because, I was watching a TV show like a doentary about those prisoners, and this one guy who was incarcerated said they did survive because, he got a postcard from them that said "Gone Fishing" which I guess he said was the secret message that they made it. What do u think?