Hi!
I have made some tests with 2 monitors to try to understand how compiz is placing windowses after second monitor is disconnected. Placement is quite strange to be honest :)
I have to note that the same happens in compiz 0.8.x as well, so functionlity might be the same.
I defined 3 (horizontal) x 2 (vertical) workspaces, I connected second monitor, I placed 2 firefox windowses on each workspace on each monitor. I called windowses like this - "wsX monY win" and "wsX monY fs": X = workspace number, Y = monitor (1 - laptop internal, 2 - external), fs = fullscreen window, win = regular window.
When I disconnect monitor I press Fn + F7 on my laptop, that will redetect monitors (as far as I know) and window placement is somewhat not correct, here is the listing of windows and where they went after disconnection of second monitor :
ws1:
ws1 mon1 fs
ws1 mon1 win
ws1 mon2 win
ws1 mon2 fs
ws2 mon1 fs
ws2 mon1 win
ws2 mon2 fs
ws3 mon2 win
ws2:
ws2 mon2 win
ws3:
ws3 mon1 fs
ws3 mon1 win
ws3 mon2 fs
ws4:
ws4 mon1 fs
ws4 mon1 win
ws4 mon2 fs
ws4 mon2 win
ws5 mon1 fs
ws5 mon2 fs
ws5 mon1 win
ws6 mon2 win
ws5:
ws5 mon2 win
ws6:
ws6 mon1 fs
ws6 mon1 win
ws6 mon2 fs
I expect that if I remove the monitor windowses remain on the same workspace on visible area (laptop screen).
All software details are there: https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/920650.
I'm using ppa:vanvugt/compiz and ppa:vanvugt/unity, so I could not make bug report with ubuntu-bug.
Status changed to 'Confirmed' because the bug affects multiple users.