Welcome to the forum. :)
I don't know, but think we can try to figure this out without getting a photo. I like the challenge. And Yay! that you have no cell phone. There's not many of us around any more.
I found an image of the tulip tree leaf, is this similar to what you are seeing?
How tall is this volunteer right now? If it is young, the seedling's leaves may end up looking nothing like the mature growth. If the plant is in a spot you do not mind, just let it continue growing for the time being.
Tree seeds can come from a long way, but have you looked around your neighborhood for anything similar?
Another thing you can do is find your extension office and likely you can mail (or take in) a leaf for identification. Just call them first as they can direct you the best way.
I hope your mystery gets solved one way or another.