Notts will definatly miss Heffernan, who finally got Notts' first goal of the season last Saturday.
Speaking to the Nottingham Evening Post, Heffs said:
"It was a bit of an up and down week for me to be honest, getting sent off against Peterborough and then scoring the goal. But I didn't think I deserved to be sent off. 
"I did raise my hand, but I barely made contact with him and it wasn't with his head or face either. He had given me a tug and I was just trying to shrug him off. But he went down very quickly.
"I guess it is just a lesson you learn. It was very disappointing. It was his reaction that got me the card.
"It would have been okay if it had just been the rest of the Peterborough match I had missed.
"I thought we still did enough to win that match, we were the better side. But I now have to sit out another three games as well.
"There is no hope of an appeal, because the video doesn't show the incident. Now I am going to be out just when I want to be establishing myself in the side."