@JaneJeffer - it makes me think of that as well.
After last night I have decided that Lachy has possibly killed Rebecca but nobody but Ross will notice. If she's not dead then he will have her locked up somewhere, either against her will or because she can't remember anything again.
Lachy will tell everyone she's taken that job offer in Ibiza that was conveniently made by a friend she's never mentioned before just in time for her disappearance.
Everyone will think she's gone on the run because of stealing those cars that were also conveniently appearing for the first time just as a reason for her disappearance might be needed.
Only Ross will think there's something wrong and keep looking for her. Everyone else will blame the cars and the memory loss and just accept she's gone, not care that she might be vulnerable, and not bother to look for her.
And when he gets too close to discovering what Lachy has done with her (killed her / tied her up and kept her in a convenient outbuilding just like the cars / popped her in a private hospital with memory loss / whatever) then Lachy will kill Ross and that's how Sarah will get her new heart.
I hope he also kills Daz just as a favour to the rest of the world. That article about chasing people and biting them is weird.