I had exactly this problem a couple of weeks ago, though fortunately I was collecting a few days before travelling (I don't trust TOD enough to collect on the day). The tickets were shown on the system as having been issued, although nothing had come out of the machine. The ticket clerk wouldn't help because the tickets had been bought through (my employer's) travel agent and he said they would have to reissue them. The travel agency said the ticket office whose machine had run out of paper should override the system and issue the tickets. It took me a whole afternoon of faffing about, phone calls and emails, and another trip to the station, before I finally collected the tickets six hours later, and even then the ticket clerk took some persuading. I think it's ridiculous that the ticket machine cannot tell you it's short of paper BEFORE you put the reference in, since once you do that the database thinks they've been issued.