Nut Fluke?

The kids ran into the house with excited screams. They had found the biggest acorn ever and it was cause for celebration. They brought it to me and to my surprise it wasn't an acorn at all but what I believe is a hazelnut. So, we donned our coats and set off out to find where they had discovered this amazing nut.

We tromped through the forest and dug around the bases of at least three dozen trees before stumbling upon a treasure trove of them, all at the base of one particular tree. The girls raked the blanket of crunching leaves away and plopped nearly two dozen into our basket. But here is the odd part...I'm fairly certain that tree isn't either a hazel or chestnut. I pulled a leaf from both the large tree and smaller bush that were the only two for yards in the area and compared them to Wiki's photos.

So, I'm asking for your advice or insight. Did we stumble on some odd nut fluke (no one has lived here for a few months but us) or are one of these leaves actually from one of the trees these nuts could come from?

Also, if you know, what are the nuts anyway? (Don't mind the smaller acorns, those were Emmy's contribution to the basket since she couldn't find any of the larger nuts)