1994 subaru legacy taillights/licence plate lights not working

[Alexhagen]

So I just bought this '94 legacy today before I went to work, I got off work tonight and was leaving and got pulled over because I had no lights in the rear, signals worked, I turned off the car, well while he was standing there i started it again and all the lights worked, do you think it was because it was cold? maybe a fuse? I will look around in the morning but thought I would ask before the morning.