Jon Daly's second-half effort was adjudged not to have crossed the line but McNamara took a different view. United captain Daly had diverted John Rankin's shot goalwards in the latter stages of this contest, but Inverness goalkeeper Ryan Esson got a touch on the ball before reaching back to grab it underneath his own crossbar.
From his position in the dugout, however, McNamara thought a goal should have been awarded.
He said: "From the angle I was at, it looked as though the ball was over the line, but the linesman has not given it, which is disappointing.
"I thought we merited the three points. Over the 90 minutes we were the better team, especially in the second half, but we just didn't take our chances."
Having spoken to his goalkeeper Ryan Esson, Caley Thistle boss Terry Butcher believed referee Brian Colvin was right not to award the goal.
He said: "Ryan Esson is adamant that it was not a goal.
"I think both teams didn't do enough in the final third, but it was still a great game with good passing and movement from both teams."
Inverness dropped a place to third in the Clydesdale Bank Premier League table as a consequence of the stalemate and Motherwell's victory over Celtic.
But Butcher said: "If you look at the other results tonight then it's a good point for us. I'm very pleased with the effort the boys put in."
- Sports & Recreation
- Ryan Esson