I'm probably late on replying to this. Check to see if there are any "latch" markings that are broken off, etc. If there is a single latch that is broken on it than there isn't much you can do. I haven't found a good source of replacement keys w/ latchings (and if its broken off of the actual keyboard layout then yer really SOL).
What I've had to do before was actually call the mfc. of the laptop and have a customer pay for shipping/part cost of a new keyboard layout, dissasemble the laptop and install the new one. This is the worst case scenario because he had a 3-clip system that was based on the layout and all 3 clips had broken off.
If you don't have any broken latches then reattaching should be relatively easy, just kind of align the two smaller items first and get them onto the board, the button can go on last and usually theres a certain direction you want to pressure it towards, you don't want to push too hard because then you'll be back at square 1 with broken latches.