Paying for Free Parking
It seems like scammers are always out to get out-of-towners since they’re easy prey. The OP and his dad were visiting Austin and wanted to see the bridges where thousands of bats fly out from. They spotted a parking lot near the bridge and a person sitting in front taking money.
They gave them $7 to use the parking lot but when they came back after half an hour, the mysterious person was nowhere to be seen. Only the chair they were sitting on was left behind and it was conveniently blocking the “Free Parking” sign. Sure, $7 is not a lot but it all adds up.