'No suspicious circumstances'?
If everything is as we have heard - average guy, nothing dodgy, on night out with pals, not drunk, no mental health concerns, not depressed, on way home on train - I would say it is WELL damned suspicious.
He's on a train going home, sends partner text about something going on, gets off in a town that he knows no one in, starts walking around- then weeks later found dead in the canal.
I think the tox reports might show traces of something that affected him, because this is far from normal.