I think you guys are mistaken about Rey being hidden from Ren. I think it’s more likely that Ren is the one who dumped her on Jakku. Ren was Lukes star pupil and likely successor to lead the new Jedi order. Then baby Skywalker is born and is a force prodigy. Ren is pissy about being cast aside and hooks up with Snoke. He’s ordered to wipe out the Jedi order and bring the Skywalker child to Snoke. He decides to kill her instead because he doesn’t want to be second fiddle again but can’t follow through, so instead ditches her on a random planet. She doesn’t remember any of this yet.
Kylo Rens reaction to hearing about the Jakku escape and fear when she starts to realize her force powers make no sense unless they have history, and his inferiority complex makes no sense unless he’s been cast aside before in favor of Rey. It also would completely ruin Luke’s character for me if he abandoned Rey to the same life he had been stuck in, and then gave up fighting for good.
I really like this as a possible explanation.
There’s also the novelization. When the lightsaber whizzes by Kylo and into Rey’s hand, he thinks “It is you”.