Are you kidding? You forgot that The Ball also lives here.

[ In other words - there are always things around to gather evidence with. Fabian knows that Riz is keeping a whole lot of it in his room after the whole clue board incident they were dealing with the other month, but it's not like that room is infinitely large. There's just no space for all of it.

So when he opens up one of the cupboards, luckily at an angle where Gorgug should easily be able to see it as well, it is full of evidence containers in all shapes and sizes. ]

Really, we could be running a lab here. In fact, I am fairly certain The Ball would, if only he had more space.