We don't know how far he got, where the other witnesses were/ or all the vehicles. They haven't said he didn't leave on a bike, he didn't leave on foot (in between the lines, he could have
Left on a bike and that is the last footage of him). Highly doubt it, but likewise possible.
He wouldn't have gotten very far. Let's face it, if tony is absolutely certain Corrie couldn't have left on foot without been caught on cctv it stands to reason that you can't leave that area on any mode of transport unseen. If they have ruled out one they have ruled in his mode of transport.
Any individuals that are unidentified will have almost certainly been ruled out as being Corrie, Tony has said today they're able to analyse gait, limb length, hand size etc etc in order to determine if Corrie may be an individual seen.
It stands to reason in that case if he left on a bike, he was seen and they would know.