Now you know your not supposed to be driving by OWs. And you know you are not supposed to assume. Why do you think they went our of town together? Wouldn't they only need one car IF they went out of town together. OW was probably at work and H was probably at a job site or one of you many properties.
Have you ever thought maybe he spent the time you were away at your own home? Or maybe he took off out of town alone to think just like you did? Maybe he went back to his parents. Maybe he flew to Vegas?
See where I am getting at? The possibilities are endless which is why it is not a good idea to assume.
I wanted to say I thought it was a good sign your H went to your home the other night. That is a sign that things between him and OW are not as tight as you may think they are.