I am trying to book an ICE ticket from Frankfurt Airport to Dusseldorf. Plenty of trains available on the date I want, and for only 29 Euros. If I book for him, I have to enter his ID, and the only acceptable forms are credit card, Bahnhof card, Maestro card, or ID card, none of which he has. (He has a passport, of course, but that's not an option).
I don't want to buy the ticket and have him stuck unable to use it. Any suggestions?