People are questioning what 'seeing' an incident means it is quite clear it is off the ball incidents that the ref is not looking at and therefore doesn't see.
If you can now say the referee is looking directly at an incident be it a potential foul, penalty or violent conduct but the ref is looking at it but does nothing at the time effectively every club can present video evidence on pretty much anything where they disagree with a referees judgement at the time.
Mariner was looking directly at the incident and didn't judge it worthy of any punishment, free kick, booking, sending off. That should be the end of it under the FA's own rules...,,