My son's cat caught and released a mouse at least half a dozen times this morning before he finally got bored and walked away. The mouse escaped. Later the cat came back to search where he'd left the mouse. I think he expected it to still be there.
I read an odd theory on why cats play with mice - they don't do do with all food sources. It said the mice don't taste as good and the cat needs to build up an appetite. Note, I don't really believe this, but uh, who knows; or they just enjoy the torture aspect. I do love cats however.