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?
https://en.wikipedia.org/wiki/...
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.
