I own a few shops with cctv in them and agree that if we spent time simply watching cctv for all minor offenders then we would never get any work done! Unless your friend is a persistant repeat offender, then you will not be on their radar and it is probably company policy to ban all thieves in this manner in attempt to stamp it out. If your friend is a persistant offender at shop lifting and you want a career in law, then you need to question why you are keeping such company! As another poster has suggested, why don't you write to the shop, expressing your regret and ask if they will accept your apology. As a gesture, you could offer to pay for the shoplifted items if they were not recovered, if they were, you could offer to pay this amount to a charity of their choice. I am sure that if a customer wrote to me in this manner, I would want to look upon this favourably.
Best of luck and as the others said, you have already spent enough time agonising over this, if you cannot take the steps to try to put it right by contacting the shop, then put it behind you and move on.
Cheers Sue