Should A.rsenal's 3rd goal stood?

[Brin]

Seen the game tonight with Man Utd and De Gea has the ball in one hand undecided whether to kick it or throw it.

Before he knows what's happening, Aubameyang runs from behind him and heads it out of his hand and taps it home for a goal.

According to Gary Lineker on MOTD, the Ref never saw what went off, very poor officiating and, where was the linesman in all of this?
The Ref cancelled the goal ??? Why if he did not see what happened ?? Surely he must have had a buzz from the assistant linesman.

The rules as stated by the FA clearly states that, 'A keeper is considered in possession of the ball when he holds the ball with his HANDS, it is in between his body and the ground, or when he is bouncing or throwing the ball in the air'

De Gea dit NOT have the ball between TWO hands, it was not between his body and the ground as he clearly had it held out in ONE hand.

A total farce by the REF for not seeing this happen, furthermore the assistant Ref, (if he buzzed the Ref to update him) doesn't know the rules.

Very very poor officiating. What's more baffling, with it being such a debate, why didn't Lineker and co not discuss this??

As a previous Ref I would have let the goal stand as it was well within the guidelines.

Anyone remember Andy Crosby v Andy Dibble...Notts Forest v Man City ....Crosby's goal stood and the rule hasn't changed since.