I wasn't aware... the Manyoo players weren't, either, judging by their reactions.
If a player loses a boot on the pitch and they are involved in the play of the match they have to go back off to put it back on and an indirect free kick is given to the opposing team where the incident occurred.
It is an actual rule.
LOL at Rafeal, what a ****ing mug!
What a daft rule. I remember Gazza scoring with his sock for Spurs (against Arsenal?) back in the day.