Walnut

Why do I keep finding walnut shells in the garden? It's not me cracking shells back there. Are the crows doing this?

Then yesterday I was pulling out what looked like weeds, and one of them was rooted in a walnut shell. I was growing a walnut tree, until suddenly I wasn't.

A couple hours later I went back outside with a cup of coffee and the third issue of Rob Manery's some magazine. Both the weed and the shell were gone. Did a crow take it?