Colorado resident Mitch Gilbert was flying out of Las Vegas when he found two unmarked Caesars Palace envelopes. When he got home, he opened them and found the cash.
After numerous calls to the airport, the operator finally agreed to take down his information since a man from El Paso, Texas, had reported it missing.
"I wanted to show my kids the right thing to do," Gilbert said. "I think he was pretty much in shock. I don't know if he believed it."
Ignacio Marquez, who lost the money, said he knew the odds of someone returning $10,000 were pretty slim.
"I will always thank Mitch for doing this," he said.
Marquez said he won the money gambling and dropped it as he was running to catch a flight.