Has anyone seen this cheat? Am I crazy?

I was in ultimate arena when I saw gems flash over a player. Instantly the gems disappeared.
I thought that maybe they had been grabbed so I left arena and came back a couple of times but even reloading didn't change the order of the players.
When I hovered my cursor over the player, it showed that they still had 10 gems. I hit the player and received nothing.
Has anyone seen this before?
Am I just crazy and seeing things?

My first guess would be someone else took them first... once they've been taken, the gems don't show, but if you scroll over the player it will tell you what they have until the clock runs out.