You and Mary are in the same timezone, I am working late across the pond from both of you. I will jump in incase you are up late
It does not sound to me as if certificate has been installed. It is contriburted code so it does not come with the standard Moodle Install which most hosts provide. Have you been able to create a certificate activity in any of your courses, without your College's logo of course?
Yes it should be in the /mod folder, in a sub folder called certificate. There will be other folders inside the certificate folder. Maybe somebody put the folder and it's subfolders in the wrong place.
Guess a host could tweak the code and do something else with it. Check under site administration > Modules> Activities > Manage activities. Likely if you can not add a Certificate activity in a course that you will see it here.
Since you have FTP, you can install it yourself. If you are not feeling brave (and your host will not help you) and want to practice, my mantra is to practice on a localhost. As your college's expert, I hope you have a couple of sandboxes (localhosts) like me to play with.
Hope this helps. I think this is what Mary would tell you as well, except without the Yank accent