Apparently this story is getting a lot of talk. If you look at it from Frank's perspective, that bass was way too small to have eaten it on the initial drop some 21 years ago. So that would lead us to conclude that the ring was lying around on the bottom and after many years (perhaps) a bass just decides to eat it. Maybe the sun just hit it right that day. What if the bass was spawning and made a nest (unknowingly) right on the location of the ring... then while the bed was being fanned out by the male, the sediment was washed off the ring making it once again visible and then the sun hit the ring... this could have triggered the 8+ lbs female to eat it...
or, maybe the "anonymous" ring finder finally decided to return the ring to its rightful owner...
All that's missing here is some Hobbits, two wizards, a lot of elves and a big eye in the sky fighting for control over "Middle Earth"... after all in JRR Tolkien's book, didn't Sméagol and his friend find the "RING" while they were fishing and then Sméagol killed his friend over the "RING"? This might explain why the person returning the ring to Joe wanted to remain anonymous...