The problem with breaking the law is that you can be nicked.
Thats the way it is and I believe if you make the choice you take that chance and the bong just gave them probable cause to search.
Do the crime do the time.
I'm so glad the English cops are more laid back about this sort of thing, I've had cops in my house which is full of bongs and hookahs and the cops wouldn't think anything of it, you're just in a country that is far to uptight about ganja.
Last year I got arrested for ABH (actual bodily harm) and I had 2 oz on me at the time and all I got was a caution.