I'm a lot older than you, but I have a similar situation that I would like to share with you.

I was married when I was 22 years old and we had a yellow Lab named Chuck. He was a wonderful boy and although he was truly my husband's dog, I was his primary caregiver, feeding, walking, etc. When we seperated, I was so concerned about Chuck and wanted to take him with me, but it wasn't meant to be. Our cat, Mimi, went with me, and Chuck stayed with his "dad". There was never a time in the following years that he didn't "know" me when I would go to pick up my daughter or drop her off at her dad's house. He always "knew" me, or at least he acted like he did! I loved that dog and he lived to the ripe old age of 15 years.

Your Sammy will be the same way. He will know you and you will have him back! I don't think they ever forget people who love them.