( - A man who dozed off on a flight from Louisiana, awoke to find himself cold and alone on a locked plane.

Tom Wagner was on his way to visit his sister in California. He decided to take a nap before his layover in Houston, and continued to sleep as the plane landed and the other passengers disembarked at George Bush Intercontinental Airport. Somehow the flight crew did not notice the sleeping Wagner and left him on board as they locked up the plane, the ABC affiliate KTRK reports.

Wagner found himself sitting in the dark on the empty plane and discovered he had been locked in. Luckily, his phone was working and he was able to call his girlfriend, who then contacted United Airlines to tell them Wagner was trapped on one of their flights.

"She thought I was crazy," Wagner told KTRK. "I said, 'Debbie I'm locked on the plane.' I said, 'I'm telling you the truth; you better go somewhere and get me off this plane.'"

About 30 minutes after she contacted the airline, employees opened the door.

Although the airline would not refund the ticket, it gave him a hotel room for the night and provided him with a $250 voucher to help Wagner complete his journey.

Wagner was on a United Express flight operated by their partner, ExpressJet.

"ExpressJet is investigating to determine how this occurred. We sincerely apologize for the inconvenience this caused for the passenger," the airline said in a written statement.

Wagner still has many questions for the airline. "What if I had a medical condition or something?," he asked. "What if I had a heart attack and I was dead? You just shut the plane and leave someone on there?"

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