All I can figure out is that something ate them. What could it be?

They were completely eaten? Are they near the shore where land animals can get to them? Here are some possible suspects if you have them in your area - deer, muskrats, and people. Actually, I can't think of too many but there are more I'm sure.

Not even a leaf to be found. And, yes, they were by the edge. It was just so odd to me to look and see no plants at all.