Maybe they thought they’d leave her there for a few hours. I mean, given the final timeline we’re looking at it seems Ochi was right on their tail.
Rey could’ve come to see herself as having been “sold,” but the idea doesn’t need to be in this movie. That term need not be hung on it, I mean. If you want to describe what happened in TROS’ depiction of the past, it could be described other ways. Maybe they paid Unklar a little something to watch her a while.