Like Master, like apprentice. ;)
Rey wakes up after the strangest dream of all: she saved the Supreme Leader from a coup on Coruscant and now they're stranded on a peculiar planet, soaked in the Light Side of the Force. She wraps herself tighter in her cape and turns to the other side – and then she remembers.
She jumps in the little bed and hits the low ceiling with her head. As her eyes settle on the floor and pain subsides, she realizes he's not there. But there is a pleasant smell of a small fire and something resembling food on the outside and she is covered with her cape – practically tucked in.
Strange things seem to never cease.
She walks outdoors to find him hoarding old fuel canisters. He washed away the coagulated blood and the dirt from his face and from his clothes for the most part. His shirt is partially unbuttoned and he looks as casual as it is possible for a Knight of Ren in his ceremonial robes.
He left some of that clean water to her and she rubs her sleepy eyes with the edge of her arm wrapping. As she goes about her business, he informs her about his finding:
At the crack of dawn, he found them – not nearly enough for a long voyage, but enough for the nearest outpost and for communication; buried in a hollow under a tree and camouflaged with hastily stacked rocks.
"He left everything behind to get to Vader faster", he says that more to himself, and rattles the canister so he might evaluate the volume of the remaining fuel. "I remembered it only later. He spoke about Dagobah, but was never particular about the details".
He almost smirks as if to say: Dishevelled old fool.
"He left everything behind so he might save his friends", Rey utters. His need to undervalue the old Master pains her, but at the same time, that pain gives her the necessary focus in the Force.
He is again startled. This is not a detail that is commonly known, especially among the scavenging population of Jakku. He forgets how strong she gets with time, and she can't blame him for it. It comes at her as a surprise time and time again.
"I'll fill it up", he says, quickly changing the subject. "You eat".
Grilled snake-like creatures (whose lair he shook to get to the canisters) and bugs impaled on a wooden stick with some indiscernible vegetables on the side, placed on leaves – the smell is far from appetizing, but she ate almost nothing since they landed on Coruscant, and the strain of the escape left her famished.
Before she manages to thank him, he's already gone.