OS X creates swap files whenever it needs to. It could have happened at some other point during the last day. If you don't have a ton of RAM, and you keep a lot of apps open at once, or use a memory hog like Photoshop, you'll get quite a few after a while. (2 swap files is just no big deal) Just keep an eye on your available hard drive space-- if it gets below a few hundred meg, things will get weird.
CV