Thank you for doing right by the snake. I recall a thread a couple years back, posted by a young girl (15?) who had found a Ball on her way home from school, one that turned out to likely have an RI. I think, IIRC, a relative came and took it from her, but in short yes - people WILL let a snake loose if it will be more money to treat than they think the snake is worth. A new normal BP is cheaper to just buy than the vet bills to treat it. A crappy mentality to have, but it does happen, poor snakes.
Thank you again for helping this poor little guy along! A grocery store parking lot at Christmas. How terrible! Glad you were able to find help. Happy holidays!!