Imagine Grillby finding out reader uses a heated blanket to try and mimic his warmth when they miss him when he's gone at work or something.
It had been a long night. Doggo had a few drinks to much and had refused to go. Whining about how he had no job since sentry stations weren't a thing on the surface. Grillby had to call Sans to escort him home, and the skeleton patted the dog monster's back.
Now he finally was on his way upstairs. He loosened the bow tie and opened the door quietly. He had expected you to be in bed already, slumbering the sleep of dreams, so he was surprised to find you snuggled up on the couch the TV running silently. He sneaked closer, and as he saw you completely he had to smile. Your arms were wrapped around a white blanket that emitted heat, clinging to it in your sleep. He knew that position too well, you held him like this often enough when you two cuddled.
With an inaudible chuckle he stroked your hair, and you sighed happily. So this is how you kept your heart at bay when he wasn't there, a blanket to remembered his warmth. Gently, to not wake you, he pulled the blanket away from you, only to replace it. You woke up a bit, mumbled something in a happy tone, and wrapped your arms around him. A peck to your forehead, a hand on your head. Then you two fell asleep.