'A few posters have said they think it's concerning he is walking fast in the cctv footage. Do we know the time of that and what direction he was walking in? Could he have been walking to the bus and walking fast not to miss it?'
Well if he's feeling unwell and wants to relieve his bladder or bowels maybe he's getting a move on to either get back to where he's dating or go hide behind a rock.
Later on if he's left a path to relieve himself without anyone coming across him then he may have slipped, fell or fainted/died whilst doing so.