Perhaps because she'd been in her parent's friend's apartments that week and just may gave thought her parents were there ?
BTW Alfie if my argument is so pointless why are you using so much energy trying to discredit it ?
When did Madeleine go to Jayne's apartment that week plz?
IIRC you originally asked why Kate didn't go to JT's apartment to see if Madeleine was there.
IMO Faith there are several reasons why JT would not even enter Kates head at the moment when she found her daughter was missing:-
JT was not involved in the McCanns checking arrangement.
JT was not a close friend - having only met the McCanns half a dozen times in the 4 years she had known them and Madeleine would hardly know JT at all before this holiday - so was not likely to think of her as someone to go to.
JT had never been in McCanns apartment - so no prior 'connection' there to make Kate think of her.
JT would not have taken Madeleine out of her apartment without letting her parents know. But even if she had - Russell would know because the only time JT could have done that was on her way back to take over from him so that he could go and have his meal.
I'm sure Kate's mind would have been racing with all kinds of thoughts from the moment she found Madeleine had gone, but I doubt very much indeed that Jayne Tanner was one of them. It's just far too unlikely IMO.
AIMHO