Found a bat in my house. Story inside.

So in the middle of the night I heard a noise that I thought was some kind of bug. After 10 - 15 minutes I realized that whatever it was wasn't going away on it's own, so I got up to shoo it away. This little guy was on the floor screaming at the slider door being harassed by my two cats. I don't have a chimney or attic, so I have no idea how they got inside. When I opened the door, instead of taking flight, they simply hopped out the door froggy style. Were they injured? I don't think my cats did it if so, because they mostly just seemed confused by the poor creature. And what were they doing in the house?

Additional pictures of my unexpected guest being rudely gawked at by my feline friend:

And yes, I'm taking my cats to the vet just in case they got bitten.

UPDATE: Thank you to everyone concerned. I have contacted a doctor and she said that given the full details of the story I shouldn't need to worry. The poor thing was inside for *at most" an hour when everyone was awake, so it's highly unlikely to have bitten anyone before being spotted by me. The only concern remains the cats, who as mentioned found the bat before I did. I plan to vaccinate them ASAP. Once again, THANK YOU, but doc says I'm fine.