A crescent-shaped light that seemed to be cut off by going behind something.

My girlfriend and I were sitting on my front porch and she observed a crescent-shaped light that was brighter in the front and dimmed as it moved through the sky, going West. It faded away as if it were going behind a building.
She got my attention and I looked up from my phone. My phone was bright and it was dark, so it was hard for me to see. However, I saw what looked to be the moonlight behind the clouds, but if it were on a night where the moon were particularly orange. I looked away to let my eyes adjust to the night and looked back to discover that it was gone. I looked to my south-southwest to discover the moon in the sky. Whatever we saw was not the moon.
I have an app on my phone, Flightradar24. It’s fairly self-explanatory but it is a flight radar. I’ve been able to track planes, public and private, as well as helicopters using this app for about two months with ease. If there’s a plane in the sky, I can tell you where it came from and, if it has a destination, where it’s going. I immediately checked this app to discover no nearby planes. No nearby helicopters. Nothing in the sky that was being picked up on the radar, not even a balloon (which I’ve also been able to see throughout the country.)
Unfortunately, I was unable to get any pictures of this, but I wanted to report it in case anybody else saw it and decided to do the same thing.