Was the bong dirty?

Was there weed in the house?

Because if it was clean and there wasn't any weed you could have surely told him that he cannot simply come into your room and start searching, since he wasn't invited in and he wasn't given permission. There's another thread here I read that was really good on making quite clear what your rights are when it comes to police encounters.

You shouldn't have admitted to having smoked anything, mate. I hope things work out for you though, read up on that other thread and see what the people here say(since they are American and will know your law better than a Scotsman does :P)

All the best dude.