Don't ever leave your campsite unattended in a National Forest on a holiday weekend. It is typical for a forest to fill up with campers during that time, which brings out organized gangs of thieves who rove around looking for opportunities. If you need evidence of people being robbed in National Forests, notice the bits of broken window glass on the ground at various trailheads.
Anyways in my 1st season I was camping in the Pisgah District of the Pisgah NF to the southwest of Asheville NC. It's a rather popular forest even in regular times and on Labor Day weekend it was packed. I had left my campsites unattended when going into town for a couple months before that, no problem, in both the Pisgah district and Grandfather district to the east of Asheville. In fact I thought my site in Pisgah was pretty spiffy because it was right next to the main highway and I could zip into town easily for supplies. Well that also makes it easy for thieves to zip up to you. I went into town to get a mug from Walmart so I could make decent tea. The mug cost $2.50 and I later named it the "Black Mug of Death" because that trip cost me $500 worth of stolen camping gear. I got back to my site and this multi-generational redneck family had set up with 3 tents, tarps, grills, seriously heavy footprint stuff. I was miffed and said, "Didn't you see my stuff?" The old timer said, "What stuff?" Oh boy, sinking feeling. No reason to believe they took it, the gear they had in evidence was far more valuable than my paltry site.
Filed the police report. Never got a phone call about anything being recovered. Police confirmed organized thieves in the area. Stands to reason: my site was almost perfect for stealing. My camp itself was out of sight behind a small dip by a creek. I figure a 2 person team pulled up. One does lookout in the truck, the other grabs everything and shoves it in the truck. Cleanout in 10 minutes easy. No sorting, they even took a worthless homemade instrument I made out of a bowed stick, a string, and a plastic lemonade bottle. They took plastic bowls and silverware.
Ever since then, the drill in a NF has been (1) avoid holiday weekends, (2) park FAR down some horrible road, several miles of bump, grind, and difficulty, to make any would-be thieves really WORK for their opportunity to rob me. They aren't gonna get anything by just casually cruising around.
Also to be honest I just don't leave anything at a campsite anymore, because I don't tent camp anymore. The car is the tent. Saves me at least an hour of setup and breakdown time per day, if I'm wanting to move more than sit still. Any given region in a NF can get boring in 2 days, they all the same logging roads for the most part, so mobility is good policy AFAIAC.