Whole Foods...Partial Idiocy

I went to one of the two (and soon to be three) Whole Foods stores in town tonight and the cashier who rang up my groceries have me a hard time because I paid for my items with an older $20 bill. I guess she thought it looked suspect or something so she called another guy over to see it and he proceeded to use use his super counterfeiting skills by running a yellow highlighter over the bill. (A real Einstein here folks! Call MENSA!) Uh, isn't it illegal to deface US currency?But I digress. Eventually, the cashier and boy wonder took my money but only after humiliating me in the process. I complained to Whole Foods too and I asked for a response to this tomfoolery. I'm a law-abiding citizen, damn it!