May I see your IDs miss?

So as most of you probably know, many people nowadays are putting "Check ID" on the back of their credit cards instead of signing it. The reasoning is supposedly to make credit card theft a bit more difficult for the thief.
Today at work, a couple came in, who appeared to be in their mid to late twenties. They seemed pretty laid back, and having a nice relaxing Saturday with each other. They came in, ordered the stereotypical espresso beverages (non-fat lattes and the like). When it came time to pay, the girl handed me her credit card to pay. I swiped the card, and then checked the back like I do for all credit cards to see if she had written "check ID". I check every credit card I get because once, when I did check, and the customer's card did say "check ID", and I did check the customer's ID, he thanked me saying "most of the time people don't check for ID". And so, when I checked this girl's card, instead of "check ID", she had written "see my tits", in all caps.
Now, I know most of you are probably coming up with excellent ideas on how to exploit this situation to its best, but when I was there, actually there, I couldn't think of anything to do except maintain my composure during the transaction. Had they come in later in the day, I might've been able to think up "excuse me, ma'am, but I need to see your tits", but my mind wasn't functioning fast enough. Probably all for the best; I doubt any transaction that ends with a customer flashing an employee will end well in the long run.
EDIT: I thought up a better name for this post. Its a bit more appropriate.