The former Kilmarnock player, who was only available after successfully appealing the red card he picked up against Inverness for deliberate handball when conceding a penalty before the international break, was as surprised by the decision as most inside the stadium - although suggestions later were of his hand being in an unnatural position.
And after receiving a yellow card, Hamill's frustration was compounded when former Nottingham Forest player Commons drove the subsequent penalty past Jamie MacDonald.
Jason Holt equalised in the 56th with a deflected drive from the edge of the box but goals from Anthony Stokes and debutant Teemu Pukki took the points back to Glasgow.
Afterwards Locke said: "Unfortunately for us, there was only one man in the stadium who thought it was a penalty and he was the most important one.
"I think you can see with the reaction of players and not one Celtic player appealed for a penalty and no one in the Celtic dug-out appealed for a penalty but, unfortunately for us, the referee gives it so there's not a lot you can do about it.
"There's no point (talking to him) because at the end of the day, the decision is not going to get changed.
"The problem is you don't get an explanation from anyone and if Hamill's hand was in an unnatural position that puzzles me because his hands weren't in an unnatural position from where I was.
"It is difficult enough to beat Celtic but when you get a decision like that it makes it tougher.
"But there is no point in moaning about it, there was plenty time to get back into the game.
"I am not going to use that as an excuse and there is a lot more positives than negatives I can take out of the game."
Hoops boss Neil Lennon reiterated his desire to get Stokes, who scored his fourth goal of the season before brilliantly setting up Pukki for his debut goal, tied down on a new deal.
The Irishman is in the final year of his current contract, with negotiations ongoing.
The former Celtic skipper said: "We have offered him a contract and will speak to him again.
"I would like to keep him here, I think he has done very well. Hopefully we can get something thrashed out in the foreseeable future.
"I thought his skill for setting up the third goal was magnificent. I don't know how he did it.
"He is in a good place, his link-up play was good, he was full of running, his touch was good and he took his goal brilliantly.
"I think he is taking on the challenge of Gary Hooper leaving, and (whether he can) go on to be the number one. He is answering all the questions so far."
Finland international Pukki, who replaced Commons in the second half, spoke of a perfect start to his Hoops career following his move from Schalke.
He said: "As a striker I am here to score goals so I am happy. It was a perfect pass from Stokesy and he made it easy for me.
"It is important to score goals and it gives me confidence for the future.
"I have been here only a few days but I am ready for the Champions League game against AC Milan in midweek if the manager wants me."