In this case I think I have to agree with Cataholic. A couple of months ago I came home and there were three piles of vomit, but they were all hairballs and I couldn't tell who they came from

It sounds like it might be a hairball problem. There is a fish flavoured paste available in your local pet store that should take care of things. I have also found that since using the "hair grabber" item discussed a couple of months ago, my hair ball problem has GREATLY decreased