First option: there's a chance the the deb package is in the cache.
Go to this directory:
and look for file like this:
If it's there, you can install it by doing:
Second option: Identify your package name, and download it from any computer with a browser.
sudo dpkg -i network-manager*.deb
Open a terminal and run:
The result would be something like this:
apt-cache policy network-manager
Take note of the version detail (in red).
*** 0.9.4.0-0ubuntu4.2 0
500 http://ubuntu.mirrors.tds.net/pub/ubuntu/ precise-updates/main amd64 Packages
500 http://ubuntu.mirrors.tds.net/pub/ubuntu/ precise/main amd64 Packages
Using any OS and browser to your disposal, and go to: http://packages.ubuntu.com/. There you can search for the network-manager package, and then for the specific version you are looking.
Once downloaded, you can use a USB stick to copy the file into your machine.
Finally, boot into it, and install the package using the previous 'dpkg' command.
Hope it helps. Let us know how it goes.