Had a similar experience at Exeter. Walked out, found the very helpful chap who took my landing fee and confirmed he had my FPL. I then asked him how I would get back to airside. He gave me a chit to fill in, another laminated card and told me to show my pilot's license (you know, the pooh brown thing that is in my nav bag in the back of the aircraft) to the fascist on the gate.
Long story short, some haggling, a flash of an RAF ID card and a confirmatory discussion with an RAF Typhoon pilot (who just happened to be loitering with intent) and I made it back to my aircraft.
Of course, from now on I will carry my license with me at all times - it is a very difficult document to replicate!!