Yes, combat sports is one of the most dangerous sports to be involved in even when you are a referee. In a Max Muay Thai event in Thailand, a fighter named Gou Dakui went in for the kill to knock out his opponent but accidentally caught the referee with a leg kick in the process.
If you look at the video, the kick was definitely not intentional and it was just the referee being in the wrong place at the wrong time. After a few minutes of discussion a new ref came over to wave off the fight as Super x Sitsontidech was unable to continue the fight.
They officially announced they Dakui was awarded the win in the fight moves his record to 21-9.