I've inadvertently deleted my thunderbird.dmg, does it matter? I've inadvertently deleted my thunderbird.dmg &amp; then emptied the trash.  Doh!

Is there any way I can restore that particular file? 

I'm running Mac OS X Version 10.6.4 on a macbook pro.
If the file is in the Trash, you can just drag it back out. However, once you remove the item from the Trash it's as good as gone*. Why not just download it again?

* there are some programs that claim to be able to restore deleted data, but the chances of recovering a large file like a DMG on the system drive are virtually nonexistent