I think as long as no medical information was given out such as why they were there to be treated and such then everything should be ok HIPPA wise. Ive worked for 3 ERs and all 3 called the police if someone left with an IV line still in them. As far as the police wanting you to call when he comes back, I think that is fine, but the thing you need to tell the police is, that unless there is a medical reason , the hospital wont be able to make the person stay there and just wait on them. You can call and tell them to come pick him up, but you can keep him there unless there is reasoning, and him having warents are not a valid reason.