nothing good. most states do not have an "active" list of permit holders, seeing as alot of different cities and municipalities issue them its hard to cross reference. 99% of the time the only evidence the LEO has that you are not illegally concealing a weapon is the physical permit that you give him. odds are one of two things will happen if stopped without your permit. seeing as its not a DL and they cannot just check the computer he will most likely arrest you. untill you can prove without a doubt that you do infact have a permit. other thing that could happen is he will confiscate your weapon, charge you with concealing an illegal weapon and summons you to court. at which time you MAY be given a chance by the judge to produce said permit or face the charge. the third is he does the last stated option, but the judge revokes your permit for failing to carry it on your person and carrying a weapon anyway.
best thing to do in this situation is go STRAIGHT to OC. *if your in a state that allows OC without a permit* OR go straight to your car , unload, clear and store your weapon in the trunk untill you get home.
i had the same thing happen to me a few weeks ago while running up the 7-11 for a soda at 1am. i was about 1/2 way there when i went to check how much mula i had in the wallet and realised the wallet was not in my pocket. i slamed the brakes, turned around and rushed home to get it seeing as my permit was in it, and in my waistband was my glock 32. scared the daylights out of me but im sure now i wont do it again :-)