virtualbox appliance windows have disappeared

[neuronetv]

I'm running virtualbox 4.3.14 r95030 on a centos 6.5 64 bit desktop host machine and I have two centos appliances installed in it, one centos 6.5 server and the other centos 7 server, both vm appliances are command line only. I had a bit of a glitch with the display on the host machine and after fixing it the VirtualBox interface is still up and the vm's are still running and working fine but the terminal windows for them have disappeared. It's no great problem because I can still log in using putty but this would have been more serious if the vm's had their own desktop gui's. Is there a way to get these terminal windows back? I know I can open a terminal on the host machine and log in to the vm's that way as well but I'd still like to get the original windows back up if that's possible - without having to restart the vm's. In VirtualBox I've tried Machine/Show but it does nothing.

[Perryg]

AFAIK the only way to get the window back into the foreground is to reboot the guest ( cold boot )
There is an icon on the main manager that says show but I am not sure exactly what has happened to your system and it may or may not work.

[neuronetv]

at some point I will have to reboot the vm's anyway to do an export/backup but it's strange that the terminal windows disappeared like they did.

[Perryg]

It really depends on exactly what happened, but it sounds like the VBoxSVC lost connection with the guest and its PID.