Hi! Yes I saw the wheel…in the corner of the camping area near our big red gazebo?
I walked over to our neighbours (the other side of where you were) to ask if it was their wheel, I think they had a black gazebo with Haro Bikes written on it. He said it wasn't theirs, though I got the impression he regretted saying that when I told him I thought someone had left it behind. Told him I was going to keep an eye on it in case someone came back for it, and then take it to registration when we left.
Kept an eye on it for about 15 minutes, then I had to help take down one of ours tents, 5 minutes later it was gone. It disappeared as soon as my back was turned. Didn't go pointing fingers as I wasn't sure if the rightful owner turned up whilst I was folding up the tent.
Hope this gives you some leads. For anyone else reading, the Haro Bikes black gazebo was in the furthest corner of the camping field (from the entrance) alongside the orange rope and finish straight, a few tents away from the white transit van and caravan that was parked alongside the rope.
They may not have it, but the wheel was close to our tents and one of our bikes so it didn't look as though it had been left behind to anyone else.