I'm going to go into my friends room and discover he has a hoarding problem
Why do you want to discover his problem?
I want to make him feel uncomfortable in his own room
Friends should be honest with each other when you think they have a problem but it is not good to invade their privacy. If you need to talk to them about their problem it is better in a place that is not their safe space.
He is an adult, he should be capable of handling it. It's not very nice of him to have a room like that.
He may be an adult, but he is your friend too. Don't you think you might have a better talk if you don't go barging into his room first?