Did you happen to take any pictures with your cell phone or camera? Based on your brief description, both shingle and willow oaks have leaves that are entire (i.e., they are not lobate, dentate, or serrate). However, the acorn description you provided does not match up with either shingle oak or willow oak.
So, I'm somewhat at a loss without additional visual information.
You can always try this excellent reference manual to assist you in identifying this mystery oak: