On Valentine's Day we found a neighbor's kitty trapped in our basement. Or maybe she was feral...we were never sure. We took her to the county shelter where she had multiple seizures and had to be put down to test for rabies (we had seen her roaming a lot, which makes me think she wasn't well cared for and was already sick when we found her).

I'd definitely ask around and echo the recommendation to go to shelters to look for her. Someone must have seen her. Hopefully someone either took her in or brought her to a shelter where she is waiting for you.