This notice is from the Official 24-hour Comics Day blog:
24HCD Participants: if you COMPLETED all 24 pages in 24 hours and your venue isn't sending in a copy of your comic to the main 24-Hour Comics Day collection (not all venues do) [Please note: Mpls. 24-hour Comic Day does not send in your artwork], please send in a copy of your completed comic!
You can use the form on this web page marked "Cover Letter to Submit Your Comics to the Official 24-Hour Comics Day Collection." Mail that cover letter, along with a copy of your completed 24-page comic to the address on the form.