Sometimes it becomes difficult to catch everyone from whom you need a signature on a form. Faculty are traveling, or you're teaching when they're having office hours, etc.
If you are ever really having trouble getting a signature, please let me know. Usually I am able to secure permission to sign for faculty and it is established procedure for me to do this. You should, of course, make every effort to secure the original signature, but please don't spend weeks trying to track someone for a John Hancock. Let me help.