Could that be like my dog, Spot?
He was always such a sad dog -- in fact, he was a Melon Collie. We named him Spot, after what he did to the living room carpet. Then, someone went for some Spot remover, and spilled it on the dog! We haven't seen him since! Tripped over him a few times, but we haven't seen him!
Then he got so dirty that no one could clean poor Spot, so we had to re-name him, Stain.
But I'm sure that it has also happened to you ---- you know, shaggy dog stories.
http://en.wikipedia.org/wiki/Shaggy_dog_stories