Upvote:2
In this page you have the airport information. It seems that you need a receipt but maybe you can call to one of these numbers and they can find a solution of you:
Terminal 1, between Concourses B and C, Level 2 (Departures), open daily from 6 a.m. to 10 p.m., phone +49 69 690 73277
Terminal 1, Concourse B, Level 1 (Arrivals), open daily 24/7 hours, phone +49 69 690 70786
Terminal 2, Concourse D, Level 2 (Arrivals), open daily from 6 a.m. to 10 p.m., phone +49 69 690 72860