Already tried that, Weasley; no luck. However, I did manage to scare up a bunch of vomit-flavoured Every Flavour Beans that one of the first-years shoved in the couch cushions, they're yours if you want them.

Things have a way of turning up in the Common Room, eventually. The assignment is done, you won't need your astrolabe until next week's lesson. Maybe if you relax, it'll turn up when you least expect it.