Good on you for looking Hosh, (good karma points) and in the guy's defence he was probably freaking out, losing your board is never fun.
I'm guessing it's the one I found about a k out in front of the Mullas SLSC.
Name and number were on it so it will be returned to the owner who I have already contacted.
I downwind SUP nearly every day that there is wind from Hillarys to Ocean Reef Marina and find at least one or two each season, so far every one has been returned to their rightful owner.
It's a bit of a mission trying to complete my downwind paddle with a kiteboard onboard but I still remember how much it sucks losing a board.
Tightlines board retrieval service, powered by beer.

P.S. I still do kite occasionally and got out for a kitefoil session first.