Wrong Again?

You know that feeling when you've forgotten something, or something's wrong, but don't really know what it is? That nagging feeling that you know something ain't right... I've had that sensation most of the day. I don't know what it is.

I hope I'm wrong, because I have no clue what it could be. When I got home nothing in the house was out of place.
...
Just checked my wallet. I got gas this morning, but everything's still in there. What is it?

Gah.

I could've sworn there was a word for that feeling. After a quick search on the internets, I'm not convinced there is. Wrong again.