Have I Missed A Trick?

[Peter Grove]

A sub can do what they want when taken off, stand with team mates, go and get changed, even go home, so no problem there.

Not quite - new wording added just this year (and which was already quoted above) says that a player who has been substituted, "must go immediately to the technical area or dressing room". So they can't just stand wherever they want, for instance.

 

[Grayson]

Doesn’t say they have to STAY there though.

 

[SurreySuperRef]

If you want to report it, feel free to do so.

After the game is done its better to just observe and put in a misconduct report rather than to be directly involved.

Your local FA can work out the details, all you have to do is your part.

If you are sure that he was a player masquerading as a spectator, you should mention this in your report.

Either way they will get hit with the misconduct charge, for failing to control players or spectators.