If you read about false memory recall, it's perfectly possible.
Someone with glasses could have been attempting to interpret that night and when Murat was made arguido, it could have been assumed that it was him. It's perfectly possible that in the confusion and exhaustion that Russ had got confused as to when Murat first spoke to him (it was only later that day after all).
It might even have been John Hill at some point that someone saw running around.
Others could have mistaken David Payne for Murat.
Or anyone else as yet not identified.
In this case I don't think false memory comes into it, Carana. A man looking very much like Robert Murat, David Payne (who would not be misidentified by the other members of his party) and John Hill was identified as taking an interest in proceedings.
They would probably have been able to say, "No, I was not standing in that particular spot, smoking ... I don't smoke anyway." Or " I was never in that spot, I was in the beach area for most of the evening."
If it wasn't any of them, it was someone, so why might it not have been appropriate to make the attempt to find him, particularly as Robert Murat was elsewhere at the time and it would have been important to him if that man was identified, particularly as he remained an arguido for so long.