Vokes, 20, had only just arrived on the pitch but was left holding his head in his hands.
Record £6.5million buy Doyle insisted: "He's young and he will learn from that.
"It is always difficult when you have only just come on the pitch and haven't really had time to get into the game. I think the ball sort of bobbled on him and he didn't realise the time he had."
Vokes could have salvaged a point and Irish ace Doyle, 26, added: "This is just typical of the way things can go. How many times do you see sides like United scraping a 1-0 win and taking the points?
"We honestly believe we've enough about us to stay up."