With no offense intended, "I don't remember how I forgot to charge a customer" isn't a convincing excuse. "Our registers went down sometimes" is a cute one, but if that had anything to do with this incident that would have been obvious from the video. And it still wouldn't explain letting a customer walk off without paying, whether or not you remember doing so. I'm normally quite happy to take somebody's word that there was a mistake or misunderstanding but, unless you're about to tell us that you were so stoned that day that you can't remember anything, there's a point at which I have to say, "Please don't insult my intelligence."

When there's good cause for your employer to believe that you were stealing, your employer has every right to take the evidence to the police and to seek your prosecution. What your employer will choose to do given what's on the videotape and given its policies regarding cases of suspected employee theft? I can't answer that; you would have to ask your employer.

As for why the civil demand is in an amount greater than the value of the amount allegedly stolen? The law permits a merchant to seek a greater recovery, due to the fact that the costs of theft and loss prevention operations are not $0 - it's more than fair for merchants to shift some of that cost onto people they catch stealing.