I have been going to the wilderness gathering almost as long as it's been going on. I've only once had something taken from my site which is usualy very close to the path which has constant foot traffic so there is almost always someone about.
I had a belt kit of ferro rod, Swiss army knife lighter whistle and army can opener on a clip taken, which was annoying. I had left it on my table very near the path with all my cooking gear etc and nothing else went, so I reckon it was a youngster being a bit opportunistic. Taught me a lesson. Just don't leave stuff that might be tempting in view.
My fault entirely, I had forgotten to put it on my belt in the rush to meet a friend.
Other than that I've never had a problem in ten years or so attending this sort of event.
Just make sure stuff is either well hidden, (I often put something down the bottom of a sleeping bag, ) to make sure if anyone was furtling around my camp, the time it would take for searching they would be seen. or if it's particularly valuable, leave it locked and covered in your car.
I don't have a car, so usualy make sure I take nothing that I particularly treasure. If I do, I keep it on my person.
You should be fine. I've never normaly worried about this sort of thing. Most people are kind, trustworthy and honest. I had a couple of people gift me new bits for my belt kit when it became known what had happened. So many thanks to those kind people.
My belt kit is now fully functional again. And I have a good memory of people's kindness everytime I use it instead of a bad one.
Go, have fun and don't worry.