Snapping turtle babies in my garden.

I live in an area with a lot of snapping turtles. I have raised garden beds in an area of my yard about 30 feet from our drainage ditches where I have seen adult snappers during heavy rain/flooding from river.

My raised beds are 24" tall. I moved two of the beds and, while shoveling out the dirt, found baby snappers inside of 2 different beds. They were only about 2 inches wide. How are they getting in the beds? I didn't see any indication of eggs and they were buried about 4-5 inches below the surface. They were a little slow but were alive. I'm just stumped. There are birds of prey that will drop things in the area, but live turtles in 2 different beds sounds like too much of a one in million chance. Any ideas?