Thank You, Stranger At Wendy's

I stopped at Wendy's on the way home today to pick up two side salads to go along with our steak and baked potatoes tonight.  The drive-thru line was wrapped around the building, so I parked and went in.  It took forever to be waited on, and when I finally placed my order and put my debit card into the POS machine, it was declined.  Stupid me grabbed my HSA debit card instead of my regular debit card.  I apologized to the girl behind the counter and said I'd run out and get my debit card from the card.  The guy behind me asked the girl how much it was.  She told him $4:19" and he said he'd pay it forward.  I told him that was a nice offer but I picked up the wrong debit card and had the money to pay.  He told me to not worry about it.  I got my salads, and gave the guy a big hug and a big thank you, and told him I would definitely pay it forward on my next visit at Wendy's.