A4 Elecric windows problem

I have an A4 Avant 2003 and on two occassions in the last few weeks I have locked the car only two return hours later to find the front electric windows down. the 1st time fully open the 2nd time half open(only front are powered).On both occassions the car was still locked which rules out user error as if it the car was open then it might have been as a result of holding the unlock button on the remote control down to long which,as you will probrably know, will automatically open them. I have ruled out the kids messing with the keys etc.. It rained last night so you can image the mood its put me in. Can anyone help please