Why would they need to do more than that?
Sometimes they just listened and sometimes they went into the apartments. Judging by Russell's statement he didn't intend to go in, just to listen at the window. Was that Matthew's intention also? He had taken it upon himself to listen at the McCann's window at 9pm, purely because he was near to it;
4078 'Was that the first time that you had taken it upon yourself to check on somebody else's child''
Reply 'Yeah, I'd not done it before, it was only because, you know, I was there and I was, and it may not have happened if I'd actually gone in and checked on Grace through the room, you know, I might not have just been next to their shutter in terms of to actually have a listen, you know, I was just there, it was only like four steps further. But, no, I didn't, even though we now knew each other for the week and I felt a bit more comfortable about their kids knowing me, as I said before, erm, I wouldn't normally sort of impose that sort of check on somebody else unless they'd, erm, unless they'd suggested it. It'd be almost like a step, not a step too far, but, erm, it's not really our place to, you know, to do that'.
http://www.mccannpjfiles.co.uk/PJ/MATTHEW-OLDFIELD-ROGATORY.htm