That's exactly right and another reason it's important to accompany your pup out there and praise the heck out of them when they're still learning.chances are, he went outside with intentions of peeing, then being a puppy, his brain went oh sh!t it's cold and no ones out here with me and I think I want back in. Then inside, he thinks, crumbs, I forgot to pee when I was out there, whoops.
Even now when our pups are a bit older, I'll stand at the door to watch them if I don't go out with them and open the door to tell them good boy or good girl when they go.