Hi Elainera, thanks for the welcome!
I cannot rule out entirely that at some point later in the evening AK ended up at that spot but I find it very unlikely that he would have any need to have gone in that direction. The last evidence we have of his movements is the cctv of him walking south down Market Street at 19.41. This is in the opposite direction of North Street and the other locations of the photos guiser posted. Instead, it is likely he would have ended up at the war memorial on the High Street (I'll expand on why I think this likely later) and then, alas, we don't know where he went.
If he had turned right into the High Street and carried on walking, he would be back in familiar territory and likely recognise the junction with Station Street (where he'd been in The Lansdown Arms and the Royal Oak) and Fisher Street (The Lamb). If he'd carried on past this junction, his search for cigarettes would have been fruitless as, to my knowledge, there would have been no shop that sells them still open on that stretch (the only newsagent shuts at 6.30).
If he had turned left, downhill towards the main shopping area of Cliffe High Street, it is almost certain he would have found Waitrose and got his cigarettes, enabling him to then retrace his steps back to the Lamb or Elly to rejoin the group. There would be no reason for him to go beyond Waitrose to the river. Obviously this is entirely based on the 'looking for cigarettes' scenario.
Coming back to the Market Street cctv. I believe that he would have ended up at the war memorial because, from the cctv, it seems he has no intention of crossing the road to turn up Market Lane back to the Lamb. (Just a reminder: the Police post of this footage said he was heading back in the direction of The Lamb, which I thought was misleading). The cctv camera on the barber shop is almost directly opposite the entrance of Market Lane, yet in the footage AK is walking straight forward, no turn of the head to look over the road. So unless he made a (rather unnatural) 90 degree right turn straight after the camera, it is unlikely he went this way and would have instead ended up the war memorial. This is understandable as being unfamiliar with the town, it is unlikely he would have realised Market Lane took him back up the corner of The Lamb. You can check this out on Street View to see what I mean. Also, I seem to recall reading that there was cctv that had been checked on some scaffolding in Market Lane which contained no sight of AK, but can't be sure where I read this.
My general impression, from the evidence is that there is no reason for AK to have gone anywhere near the river but equally the fact that he has not been found on dry land in thorough searches of the town means we cannot rule it out.