Dobsonfly Larva

So I was camping and floating down a river in Southern Missouri. I was having a great time picking up rocks from the shallow river and looking at them.
Lots had deep holes in them and little bugs crawling around on them. It was a little creepy. One larger rock I found had a large hole and a big bug head sticking out of it. It had big scary pincers. The head was so big and interesting looking I thought I would get the entire bug out of the hole to see what the rest looked like. There was a thin strip of bark floating in the river I began to use it to try to pry the bug out. It clamped down on the bark and I could feel quite a bit of resistance as I pulled back. That was scary as well. The bark was too flimsy so I went into the woods and found a more ridged stick and got the bug out. I set it on top of my kayak. It again was very scary. I drew this picture from memory and later googled random things until I found out it was most likely a dobsonfly larva.