There is that lost'n'found box at the Hangar (on 1st floor). It contains an item. Try to take something from there.
This is the low-spoiler guide for "Lost'n'found item" puzzle in Mutropolis. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.