The other thing I've been thinking is that the phone could have been taken from Corrie (or picked up on the street) and thrown into a bin anywhere, and then taken in a landfill collection.
But in the first two weeks of a missing person inquiry under these circumstances, I think the police really expected that Corrie had met with an accident and that they'd find something concrete soon without needing to search the landfill.
There's a case at the moment, I think in the Newcastle area, and I haven't seen it in national news (not that look, so that doesn't mean anything) of a man who went missing and two weeks later his body was found in a river. I think that's what the police would have considered the most likely outcome for Corrie. It might not be realistic to expect landfill searches for every person who goes missing under these circumstances. In retrospect, five weeks on, it is regrettable that that couldn't be done.
There was a post asking about the three young people near the shopping centre? I came across some mentions of them in the police appeals and the time given for sighting of them was 4.20am, but it didn't say who by. It then added some details of their appearance, and those details suggest to me that more than one person saw them hanging around or they were caught on CCTV at some point.