At least there was no damage, just gives you a nasty feeling that some scum bag has been rummaging through your car!
Exactly the same thing happened to me a few months back although they only made off with about £2.50! Left my dashcam though, I imagine they didn't see it as its hidden behind the rear view mirror (or in front of it, whichever way you prefer). I'm always concious of locking my doors, it makes me wonder how often somebody is going round at night trying their luck!