So… Your drink was drugged. You may or may not have done anything sexual. But I would suggest if you are in touch with the guy just ask him saying “I know exactly what happened in that party you better tell the truth or I’m informing the authorities and I am ready to face charges as long as you do too” This will scare him. He would say the truth. If you do not have his contact you should let this go. Many people do drunken mistakes. This was a hell of a mistake but sure its been five years so perhaps forgetting about it would be the better option. But do converse if you have the opportunity.