Some ******* with a Pellet gun was trying to snipe your ass.
You have any punk kids or neighbor beefs going on? Glass sometimes "kicks back" outward when fired on from externally.
I would really search the interior for a pellet, BB or small arms round.
Anyone shooting or hunting off in the distance? Could have been an accidental strike, if you are out in the country. Inner city, random rounds fall miles away and hit all sorts of things. Especially on New Years, 4th of July etc. when dumb ***** fire all sorts of things randomly into the air.
My two cents. But, I am a paranoid retired cop. I've responded to many plate glass windows hit by birds as well, where people swear someone had shot at their place. But, it would be obvious as the impact required to shatter a auto / safety glass window is much higher than a simple single pane older residential window.
I would look around.