Guess that makes sense. Just a very weird cent. I assumed that given an acid soak after some point the design would mostly disappear, but I guess if it eats down evenly the design will still be there once its mostly gone. Definitely a keeper to throw in the "conversation starter" jar.
I honestly can't say what happened to this coin but to me the pickle barrel bit sounds the most likely. I can't believe the sand would leave 1 side so much more detailed then the other, though sitting at the bottom of a pickle barrel (tail side down) would probably result in a coin very much like what you have. Either way, very interesting find