I won't name the restaurant where a switch was made.
My son paid the bill with all new $20 US bills.
The waiter came back, handed him a $20 and asked for a different one.
When I asked him what it was about he showed me a bill with a big slash in it.
He was sure it was not one he had handed him (this one was not new).
I explained the problem here.
I wanted to call the guy on it and my son did not want to make a fuss.
I'm guessing the guy got it as a tip and pawned it off on us. It would have been better if he had been straight forward as my son will not having any trouble taking this to his bank in California.
The next time I see the owner I will report this.
I cut back on the tip.