Foster thought he was fouled when Commons slid in to make the crucial challenge, although it looked a fair challenge and referee Calum Murray generally allowed play to flow.
Aberdeen manager Craig Brown said: "I think we did enough to get at least a point.
"We actually just committed suicide towards the end of the game, it was a careless error that cost us the game.
"Some think it might have been an infringement but I would need to see it again."
When asked if Foster claimed the challenge was illegal, Brown said: "He thought it was a foul but he would think that."
Scott Vernon had a good chance in either half, Lukasz Zaluska blocking his first effort following a counter-attack, before the Englishman failed to make meaningful contact with Darren Mackie's low cross.
"I think we actually made the best chance of the game when (Josh) Magennis headed on to Mackie who crossed across the face of goal and if Scott Vernon had got a touch it might have been a different result," Brown said.
"We were a bit depleted and I thought the lads who played gave us a shift and didn't deserve to lose."
Source: Team Talk
Source: Team Talk