Most colleges have full-time administrative staff members who first receive and sort the various pieces and parts (applications, test scores, transcripts and letters of recommendation—all of which are sent at different times by different people) into each applicant’s file. Depending on the size of a college's applicant pool, this can amount to hundreds of thousands of pieces of paper that needed to be downloaded, printed, sorted and filed. That’s why it’s a good idea to follow up with a phone call to each college a few weeks after you’ve submitted everything just to make sure they have what they need.
Just call the admissions office (don’t let your parents do this for you), tell them your name and that you recently submitted an application for admission, and ask if you can confirm that your application is complete. It’s not rude to do this, and if they tell you they’re missing something, don’t panic. Just tell them you’ll take care of it right away, and don’t forget to thank them for their time. Remember: colleges are insanely busy during application season.
One follow-up phone call to each college can put your mind at ease and let you get on with your senior year.