If I find a neighbor's cat outside in 23 degree weather, what should I do?

I found my neighbor’s cat outside, with a kinda “let me in??” look on her face. I finally got her to let me pet her for about 10 minutes before scruffing her, getting the name and number on her tag, and taking her back to her owner’s door, where I knocked, but no one answered. The light is on, but that really doesn’t mean anything. I’m kinda worried that she wasn’t put out there to explore (I hope not), but rather is trapped outside on accident. But I don’t let my cats outside, so maybe she’ll be fine?

What should I do here?