McDermott flew out for a week's holiday to Turkey on Sunday after his 30th bout ended in a fifth round stoppage.
Ferocious
The referee stepped in to end the fight after Blackpool's Harrrison dropped McDermott with a ferocious body shot.
The 29-year-old said he was disappointed after a confident three rounds.
Speaking after the fight at Warton near Preston he said: "In the first round he came out like a madman but I kept pushing him off and using my jab.
"I kept picking him off in the second but in the third it turned into a bit of a scrap rather than a boxing match.
"In the fourth I got back to business and people were telling me that I won every round except the third.
"But I am really annoyed as there were 30 seconds left when he caught me with a body shot.
"It was in the middle of my ribs and it forced me to my knees because I found it hard to breathe and the fight was over."
McDermott had been confident leading up to the fight after a solid three months training programme with trainer Ray Jennings.
The pair had worked closely on the defence and power aspect of his game and McDermott said that until that point the fight had been going to plan.
He said: "I think it was a lucky punch which floored me and I could not get up."
"My trainer Ray told me I could not really do anything against that one powerful shot.
"The judges also said I was winning on points until I was knocked down, but that was no consolation to me."