With Carluke 1-0 up through Jamie Dickson, the referee inexplicably awarded a spot kick for a challenge by Tayler Jessimer, who seemed to clearly win the ball.
It was scored and the visitors went 2-1 up before Carluke grabbed an 87th minute equaliser through James Frame.
“The penalty was an absolute disgrace because it was the best tackle of the match,” gaffer Weir said.
"It was right on half-time so it gives them a wee lift. It was very, very disappointing.
"I let the referee know but he wasn’t interested. If he was unsighted, it was a great challenge regardless of from where on the park he was looking at it.
"You could clearly see that he won the ball and it’s a bad day when their management and players said it was a great challenge as well.
“We just need to deal with it and move on.
"When you’re down near the bottom, nothing goes for you.”
Weir said he was “delighted” with the three under-20s youngsters drafted into the team due to the current injury crisis.
"It gives me a wee bit of a headache now,” he said. “Because my first team guys now won’t just walk straight into this team.
"I know these under-20s boys are more than capable now. They showed it on Saturday.
"Special mentions to Mark O’Reilly, Callum Neill and Adam Lynch, who produced the goods for me.
"They kept plugging away when they were 2-1 down and I don’t know if that’s the young mentality showing.
"The energy that these young boys bring to the team now, they ran for the 90 minutes. And I thought in the end we could have sneaked it.
"I was delighted with the performance, from the full team but more so from the under-20s boys who came in.”
Rovers, 11th with 17 points from 17 games, have no competitive game this Saturday.
"I still want to get a game lined up,” Weir said. “I’m in the process of getting Maryhill.
"It’s not finalised at the moment.”