This happened once while my husband and I were long distance dating - he flew to see me and his flight was diverted to another airport an hour away due to fog. He was not flying frontier. I know it’s a pain in the ass, but it does happen when they can’t land in the fog. I was able to go get him, but I know a lot of people on the flight struggled to get transportation back to the correct airport. Sorry it happened to you, that’s frustrating!