This does sound awful. I am so sorry that you are in this position, but...Can't you keep records of going there?
Idea: If you go there next time, and your dad or anyone else comes with you. Give him 10 minutes to come down. If he does not, have the doorman make note of it. Do not wait around for him. When you go to court you can show that you made a good faith effort to bring his d to him.
I don't know. It is really hard when they come home all whacked out, and you don't know what they did, saw, or heard. Or ate!