Thanks for the advice!
I started re-training Sam with the "here" command like some of you said. It's working really well and whenever I'm around the house or in the yard and he's nearby I say "Here Sam" and he comes running to me, (so I give him lots of praise and sometimes treats) but sometimes he doesn't really feel like it so I just have to call him in a really firm tone and he comes trotting over. I have yet to try it offleash in a park but I'm going to the offleash park today so we'll see!:P