Playing catch up with the most recent comments, so forgive me if I've missed something vital ...
As far as I'm aware, Tony is adamant that Corrie left in a vehicle because the combination of public and private CCTV (that the family sourced - not he police) did not show him leave on foot but DID show vehicles in that area during the time in question. From the radio podcast he did a while back:
"But really the options are limited because from the CCTV evidence, I think it's either two or three vehicles that passed through that way in the time window that we're concerned with. So, there's not a huge amount of option here. There's a bin lorry and another vehicle that was unaccounted for - and remains unaccounted for - and one of which now, we can't confirm this yet, but we've got credible information that a car passed the wrong way up the one way street there. But we've got an outstanding vehicle, at least one at the moment."
Having said that, Tony did say on FB that he couldn't completely rule out exit on foot (although he deems is practically impossible):
"Physical tests have been carried out to determine what is possible and not possible. As a result of those tests it has been assessed that he could not have left on foot without being picked up by one of the cameras.
Can we say it was forensically impossible - no. But he would have had to have replicated a travel pattern similar to Kennedy's magic bullet, with the added complexity of temporal alignment to have done it. Discounted."
It may be that the police still haven't reviewed that CCTV yet (Nicola did say recently that they are still working through the quoted 1100 hours of footage). It may also be that the police accept he got in a vehicle then or at some other point, but willingly. I think there has to be a bit more to it before they can move from missing person to homicide - there's no evidence of criminality, no motive or means for a murder (as far as we know) for a start.