The kids and I had fun on the rides. After we ate ...

The kids and I had fun on the rides. After we ate we went to play some games. The first game booth - the basketball game - I gave the old man a $50 bill. He then goes to the back with my $50. He came out a minute later with a $50 bill and said my money is no good. it's a counterfeit, he said. I said to him - "how do I know you didn't switch my $50 bill with a fake one while you were back there. He started yelling to the other booths and so that others on the boardwalk could hear him: "don't let this guy play, he has a counterfeit $50 bill." He then threatened to call security and have me tossed off the boardwalk. It was quite embarrassing. I left the boardwalk right after as I didn't want any trouble nor unwanted attention. The kids were disappointed.
Now, normally when a cashier checks a bill for authenticity they mark the bill in front of the customer. Why didn't this old man do that in front of me? Why did he have to go to the back room with my cash to verify the bill was authentic? Why did he have to get loud with me and cause a scene? Is he running a scam that no one else is in on? Why did this old man do that? Is this how Jenkinson's want their employees to treat customers? How are employees trained to spot fake currency? My experience at the ticket booths were different - the booth attendant used the special marker to check the $50 bill I gave her and no issues there.
Needless to say I will not take the kids back there again and I won't spend my money at any of the vendors again either.