The result saw the Robins slip into the Sky Bet Championship relegation zone and the final whistle was greeted with loud jeers by home supporters.
But Johnson preferred to focus on a committed team performance, which saw his side create numerous chances.
The best fell to Tomlin, who blazed over from the spot in the 67th minute after a foul by John Mousinho on Aden Flint.
Johnson said: “I don’t know how we didn’t score, but clearly we have to stop running over black cats.
“Lee Tomlin reckons the ground gave way under him as he went to strike the penalty and we scored a good goal just before half-time, only to have it ruled out.
“Nothing has changed as far as I am concerned and I will go ahead in preparing for Norwich City on Tuesday night.
“The fans were really supportive today and I understand their frustration at the final whistle. The players gave everything and we just needed a break in front of goal.
“I can’t find much fault with the performance other than we didn’t stick the ball in the back of the net.”
Burton boss Nigel Clough was left to rue a miss that made Tomlin’s penalty look difficult.
In the 61st minute an unmarked Lloyd Dyer somehow failed to convert a low cross from John Brayford with the goal at his mercy six yards out.
Clough said: “Lloyd will have nightmares about that one. When the ball rolled across goal and past a post I could barely believe it.
“We may not be as good as some of the other teams, but there is nothing wrong with our spirit.
“The players put bodies on the line, which is the least we must do if we are to compete in the Championship.
“I haven’t seen the penalty incident again, but it looked harsh at the time. For a goalless draw, the game certainly didn’t lack incident.”
There was a moment of controversy just before the break when Aaron Wilbraham headed home for the home side only to be penalised for pushing.
Some fine saves from Jon McLaughlin and committed defending, which included three goal-line clearances in quick succession, saw Burton cling on for a point.
City threw everything at them in the closing stages, but could not muster a breakthrough.
The hosts had also failed to capitalise on a fast start that saw Tomlin rattle the crossbar with a fierce volley and McLaughlin divert a Joe Bryan shot around a post.
Burton threatened on the break and there was no doubting which side were happier with the result.