What would cause such a thing?

Been wondering this for a long time. About 30 years ago I had a 71 RR with a 340 PG 4 speed. It started missing a little, so did a compression check and it was down on one cylinder. Long story short, had to tear it down and pulled the piston out of the dead cylinder and the top ring came out in about 20 pieces. Could it have been detonation? I never heard any pinging, but the RR was used when I purchased.