Is this for AS or A2?
If you are in A2 and your grades are vital to your place at university then I suggest you should go in as if you do not get the grades then it would be easier to have the support of school if you're going into clearing!
You would have to ask your sixth form but if you do not usually have them emailed I think you'll have to go in! As by the time you've contacted the school tomorrow you might as well gone in and got them!
Is the reason why you can't go that important?