Ghost pig?

I do not know if this is a bug or if its meant to be like this but I killed my pig to get the key and now there's an invisible sprite just hanging out there. Is there a way to get rid of it? It wouldn't bother me but I was trying to buy more and it wouldn't let me buy the third pig because apparently the invisible sprite counts as an owned pig? Will I be haunted by the ghost of Truffles the pig forever? How will I feed my poor dog??? Help!