This all makes it *slightly* less likely, but I wouldn't rule it (worms) out. They can be hard to get rid of. It's not guaranteed that Ginger would get them.
You already mentioned this, I think...but on the carrier - I like one that's a little bigger than it needs to be. Makes the insertion of the unruly patient a little easier. You know Ferris' personality much better than I ever will, but you might want to get an arsenal of smelly tasty treats while you're out shopping for the carrier. My kitties won't admit it, but they are not above accepting bribes.