Secret object behind painting?

[Commando Peach]

Then you might have progressed into the Storage/Study, yeah? You still need the key to get into the machine room. :|

The key probably went somewhere when you broke the glass (which is what is supposed to happen... I dropped mine on the table and the key was pretty visible). I guess you should just look around for the key around where you dropped the glass. If you can't find it, you'll have to use an earleir save and make your glass-breaking a little more controlled.