Well... It actually is quite easy to accidentally remove it. I suppose he could have unknowingly done that.
Also, FireFox has been known to occasionally corrupt the configuration that defines the toolbar layout which results in the toolbar resetting to defaults or simply resetting with minimal functions and without the location/address bar. Not all systems experience this. Most of my systems do not do that, however one of them would do that from time to time. It only stopped doing that after I installed an extremely customized skin for FireFox on that system.
Oh it was like that when I upgraded from 3.0 to 3.5. Thought that was the way it was supposed to be, it functioned like one very long search bar. Drove me batty.
Running Windows 7 RC 7100. Could be a bug or something. Other than that no problems.