(ABC News)-- Airline investigators are looking into how a man got left behind and locked onboard a United Airlines jet when everyone else left during a layover in Houston from Louisiana.
Tom Wagoner says he fell asleep on the plane and woke up in the pitch black cabin that had landed at Houston's Bush Intercontinental Airport, the nation's fifth largest airport.
"I woke up and the lights were out. I was like, what's going on?" Wagoner told ABC station KTRK-TV in Houston. "I thought maybe it was a layover, still on the same plane."
Wagoner says somehow everyone had deplaned and not noticed he was still snoozing in his seat. He said cabin crew locked the doors leaving him trapped inside.
"I called my girlfriend, and she thought I was crazy. 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.'"
Wagoner's girlfriend then called the airline, which sent crew to the plane after more than half an hour. Wagoner says he told workers who came on board, "'Don't put the blame on me. I didn't do anything wrong here.' And then they were, like, try to hush-hush, keep it quiet."
The airline gave Wagoner a free Amenities package, which included items like a toothbrush and toothpaste, and put him up in a motel room for the night.
ExpressJet issued a statement on Saturday afternoon: "An ExpressJet passenger remained on board flight 4245, operating as United Express from Lafayette, La. to Houston on Friday, Dec. 6, after all passengers had deplaned. ExpressJet is investigating to determine how this occurred. We sincerely apologize for the inconvenience this caused for the passenger."
The airline said it had no idea how cabin crew missed Wagoner, even after a routine post-flight walk-through.
Wagnor said United did not refund his flight, but gave him a $250 voucher to help him reach his final destination in California.
"What if I had a medical condition or something? What if I had a heart attack and I was dead? You just shut the plane and leave someone on there? It's the way I look at it," Wagoner said.