The docs go to the OIE, not the departments right, and because of (I quote my ECE grad counselor) 'the huge volume of documents to be processed, the OIE will not be able to individually acknowledge new admits'. So basically, you have to wait it out. However, if the OIE finds your docs to be wanting in any respect, they will let you know, so no worries. If they don't ask you for anything extra then your application packet is good.
Also, the OIE will inform you when they send out your I20.
If you still want confirmation, email your grad admissions counselor (your dept), that's what I did. They'll probably tell you the same thing.