Windows end up outside viewable area after disconnecting external monitor with higher resolution than laptop panel

I use a Dell XPS 13 laptop which I connect to an external 1920x1200 dpi monitor at work through a displayport connection. In this configuration, the external display is set as primary display and the laptop panel is disabled. When I disconnect the monitor by unplugging the cable, the laptop panel (1366x768 dpi) switches on and becomes the new primary display. The problem is that any window that was displayed at a position that is beyond the resolution of the smaller panel (e.g. at a y-position greater than 800 pixels) now falls outside the viewable area of the laptop panel and is no longer visible. Other windows that were larger than the viewable area on the smaller monitor tend to end up with their title bars under Unity's top menu bar. In the latter case, the windows can be moved back by ALT+mouse, but in the former case it becomes quite difficult to move the windows back to the viewport (selecting the window in the spread, then using ALT+space+m and arrow keys works, but is hardly a straightforward workaround).

To reproduce:
1. Connect an external monitor with higher resolution than the native laptop panel
2. In display setup, set the external monitor to primary and disable the laptop panel
3. On the external monitor, open a window (e.g. terminal or empathy chat) and move it to the bottom of the screen, at a Y-position greater than the Y-resolution of the laptop panel
4. Disconnect the external monitor by unplugging the display cable
5. Try to access the window you just opened

Expected behavior:
1. Windows outside the viewable area should be repositioned to fit inside the smaller display area
2. Larger windows should be repositioned so that their title bar does not end up under the Unity menu bar

It would be great if this could be fixed in the 12.04 LTS version.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: unity 5.20.0-0ubuntu2
ProcVersionSignature: Ubuntu 3.11.0-13.20~precise2-generic 3.11.6
Uname: Linux 3.11.0-13-generic x86_64
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,regex,scale,place,mousepoll,gnomecompat,wall,animation,workarounds,grid,resize,vpswitch,imgpng,move,session,expo,unityshell]
Date: Mon Oct 28 07:49:42 2013
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)