Sam reached up to idly scratch at his neck. He rolled his head to one side, making a small cracking sound. His arm dropped and he scratched at his opposite wrist. He was grateful to House, for setting him up with a fix, and a little stash to get him through the night, so he could look for a steady source in the morning.
Finding that source was occupying the majority of Sam's thoughts. Even if he noticed the man walking toward him, he didn't give him a second thought. People were allowed to walk around after dark, and Sam had no reason to suspect this guuy would even give him a second thought, either.