[\You are one of his versions, you can play both for your OC and for any Sans from any AU/]
He sat at his post as usual, just resting. He suddenly noticed a glow in front of him, and then he heard the crunch of snow.
When the radiance passed, in front of him he noticed a skeleton, similar to him, but still somehow different from him, and this skeleton lay unconscious in the snow.
After looking at you for a couple of minutes, he finally stood up and walked over to you, examining you. And then he picked you up with his magic and teleported you to the house he and his brother shared. Sans laid you on the sofa, covering you with a blanket, and sat next to you, not taking his eyes off you. It's good that Papyrus won't be there all day, because he has work first, and then training with Undyne, he will stay at her house. He himself told Sans about this.
An hour or so later, you finally woke up, sitting up and trying for a few seconds to comprehend where you were now and what happened. and then they noticed Sans, looking at him in slight surprise.
"Hello, my version, I see you've finally woken up"