First Great Western (FGW) has admitted mistakes were made over tickets issued for a Boxing Day train service from Devon to London that did not exist.
The tickets for the Totnes to Paddington Boxing Day service
Pamela Thompson, from Tuckenhay, bought the tickets in November for her son, a doctor in London, and his partner to travel to Devon for Christmas.
But the couple were stranded after finding out there were no FGW trains to London Paddington on Boxing Day.
A FGW spokesman said a thorough investigation would be carried out.
In a statement, Adrian Booth told BBC News: "First Great Western is extremely concerned to hear that customers have somehow been sold tickets for services which we did not run.
"Although we always advise checking journey details before travelling, the ticket was obviously bought in good faith and this clearly should not have happened.
"We do need to investigate this thoroughly, find out how it happened, and make certain it does not happen again."
First class upgrade
Mrs Thompson has been asked to contact the company's customer services to discuss the matter further.
The couple were offered a lift to London by a member of the public who heard of their plight on Radio Devon.
"It was such a kind offer, but they had to decline it because they had too much luggage and there wasn't enough room," Mrs Thompson said.
Her son and his partner finally travelled to London on the first available train from Totnes at 0557 GMT.
"The train manager was very good and upgraded them to first class," Mrs Thompson said.
"But I just hope this doesn't happen to anyone again."