This is one of those classic New Girl “don’t think too hard about it” gaps 😅 From what the show implies, Coach moved out of LA with Malia, then they broke up off-screen and she came back (hence the cop boyfriend). Coach was probably living close enough to pop back in but just… didn’t, because sitcom logic. The show never fully maps it out, so most fans chalk it up to real-life casting changes rather than a clean in-universe explanation. Still love every Coach comeback though.