Thanks so much!

I think the power of prayer and positive thinking on here is what helped him find his way home.
It's been a week since he disappeared. It was so weird, thinking that last week I was desperately searching for a dog, that in the back of my mind, would be gone for ever. And now, he's sitting on my couch, playing with his squeaky giraffe toy, looking as cute as possible.
He's making leaps and bounds of progress in some areas, and backsliding in others.
First and foremost, last night at puppy class, we actually achieved multiple sits and downs in class!! This is an amazing feat. Before, he wouldn't even take a treat from my hand. Now, with a trio of loud children who love sitting next to him, a dog barking non-stop, and other big dogs around him, he actually came out of his shell some and we actually managed to move forward in our training there. It was amazing!
Now that I've found the boiled chicken liver, he will do just about anything, anywhere. We are working on our recall outside. I want it to be so ingrained in his head that when I kneel and call for him to come, good things happen. Hopefully we can prevent another disappearing act.
I took him outside to go potty just now, and brought some chicken liver with me. We played with sits and downs outside (another big feat! Before, we could only do obedience on the couch... Anything else was out of his comfort zone), and he's just a changed puppy. I see so much more confidence.
The bad is... He's marking inside more. It's only in my parents house, not the apartment. He's marked 4 times now. When we went to petsmart last night, he used the bathroom twice. He seems to mark 7-8 times on a walk if we go to a different place. Why is this? Is he getting a UTI? Or just acting like a boy?