Bob Walker was struck by the sliding doors when his crutch was trapped after he tried to get off the train when support he had booked did not turn up.
In a statement, Great Western Railway said it was investigating why the help he had arranged did not arrive.
Mr Walker said he suffered a loss of dignity and did not want others to suffer in the same way.
Disability charity Scope said families were facing significant barriers when using public transport across the country.
Head of communications Richard Lane said problems are often caused by poor attitudes of staff, inaccessible infrastructure or a lack of information.
Mr Walker was returning from Bristol after a medical assessment on injuries, including the loss of his leg, following a motorbike accident fifteen months earlier.
All his travel arrangements had been pre-booked by an insurance company including assistance at stations.
When he arrived at Bodmin Parkway staff initially refused to provide a ramp because of their own medical problems. It later arrived when they saw he was in trouble.
He said: "It was just a horrible and frightening experience. Being stuck in a train door is quite frightening to begin with.
"Apart from one leg missing I am fit and active and can get around quite well. There will be people worse off than I am and wouldn't want them to suffer the same indignity."
The Office of Road and Rail said they were working to find out how widespread the issue is.
A survey of 100 wheelchair users by Muscular Dystrophy UK found having to book help in advance was a barrier.

The 2011 world silver medallist and partner Robert Blair beat Martin Campbell and Julie MacPherson 21-11 21-16 to extend her record in the event.
Hamilton's Kirsty Gilmour made it five singles titles in a row with a 21-13 21-9 win over Edinburgh's MacPherson.
And the Olympic hopeful won her fourth consecutive women's doubles title.
Gilmour partnered Erskine's Rebekka Findlay to defeat MacPherson and Beith's Eleanor O'Donnell 21-17 21-7, leaving MacPherson with a trio of runners-up medals.
Prior to the finals afternoon, Bankier, who has recently moved to Paris on a business venture, received a glass rock tablet from Badminton Scotland president Dan Travers.
She said: "I had nine National titles and I suppose the thought of trying to get 10 was tempting and another Nationals meant that I would be able to play one last time in front of my family and the people who have helped me so much in my career.
"I was really nervous before the final and I don't usually get affected like that. I had a sleepless night."
It was a good day for Blair as he finished with two Scottish titles, having partnered Mauchline's Adam Hall to his first men's doubles title and Blair's third with different partners.
The second seeds beat top seeds and defending champions Campbell and Patrick MacHugh in a high-quality final. The 21-19 21-18 win made up for Blair's defeat in last year's final when partnering Gordon Thomson.
There was also a first National title for Matthew Carder after two years as runner-up to Kieran Merrilees in the men's singles.
The South Queensferry player had to come from a game and 19-17 down against Glasgow's Thomson in the final against to win 18-21 21-19 21-17.
An amputee who was caught in the door of a train in Cornwall said it was a "frightening experience".
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Imogen Bankier ended her badminton career with a 10th consecutive mixed doubles title at the Yonex Scottish National Championships in Perth.