How to take something apart
Just read a post on the vintage synth forums where someone asked if it was common to end up with "extra screws" after taking something apart and putting it back together.
It is common.. if you do not adopt a proper procedure.
When I had to take apart a laptop and knew I had to "go deep" - all the way to removing the LCD, opening the bezel, and replacing the LCD screen - I knew I had to step up my documentation while taking the thing apart.
You need a pen, piece of paper, and tape. What you do now is for every "set" of screws you remove (say, the four holding the bottom of the case on, or the 8 holding the keybed in place, etc) - you tape the screws directly to the piece of paper, and write a note next to the screws with enough detail to be able to identify where they go. Keep these little taped sets numbered as well so you know the order in which they go back in. If your object is REALLY intricate, also take digital photos of each step location.
Tada - no more "extra" screws.