I would have left it and called it a humility block, like in the old days.... LOL! It is true, it is sometimes very hard to see a boo boo. Your mind corrects it automaticly. I guess it is a mental thing ... LOL! I am not saying you are mental. Have you ever seen those puzzles like this?
Anyway, this is a great quilt. I am glad you found it before it was quilted in there forever. That would have drove you crazy.