Is my dog replacing me as Alpha?

I have been out of town on business for 2 months (first time ever). I have my wife and 2 children and a 12 year old collie sheppard mix dog at home. I have been the alpha in our house which was established at a rather young age (Dog was about 2). I recently had to leave town for about 2 months for work and a few days ago (while I was still out of town) my kids where stting on the floor with our dog and he chomped at my daughters face and gave he2r a laceration that required stitches. This behavior happened once and only once prior to be establishing dominance when he was around two years old. Could the fact that I have been gone from the house for multiple weeks have lead to our dog trying to fill the void of the alpha role that I carried?