How can I get over this feeling of NO trust?

Almost 7 years ago, my husband went to a stag party. I was home with our newborn and 1 year old. He called me and told me that the bridal party got a limo and he wanted to know if I was ok with him going to the bars... you all know where this story is going! Long story short, there were girls putting on a strip show for the guys in the limo and suckers being passed around, etc. I am certain there is more, but that's all I wanted to know. We went to couseling for a few months and for the sake of my kids, I worked through it. Everything has been great - until now. Now, 7 years later, he has a job that he has to travel a few times a year. Everytime he leaves, I feel like he's doing something that he shouldn't be. I love him more than anything. We have 3 kids together.
The problem is he "forgot" to call me on Monday night. I asked him why he never called and his excuse is that he FORGOT! I am emotionally involved (obviously) and I need some opinions, especially from you guys. If you are out to a dinner (casual, not formal) is it possible to just forget to call your kids to say goodnight to them? I know that I would never forget, but that's just me. Maybe it is possible for some people to forget? I accused him of being in the presence of someone that he felt like he could not call home. I am very confused and full of emotions. Any help is appreciated!