Tree, very orange bark, simple serrated leaf

Unsure if the leaf came from the tree, there were lots of other species in the area and no leaves left on the tree. 30 feet tall, couldn't reach any branches to look at buds. Morus?

(Illinois)

 

Leaf doesn't fit, but tree could be Maclura pomifera.

 

I thought Morus because of the 3 strong veins and crenate-borderline-serrate leaf margin, e.g. http://trees.stanford.edu/images/morus-rubra01.jpg and because there weren't any mulberries in the area. But yeah, it's practically fluorescent orange in person.