extended one-night-stand

1.A relationship that started out as a one-night stand but turned into a relationship that never should have extended beyond the one night.;2. A relationship that is one-sided in the sense that only 1 of the participants thought it became something more, while it never progressed past one-night stand status for the other-no matter how much time is spent together/how long it continues & behaves like a boyfriend/girlfriend relationship