Permissions – Where is the Sudo Group or is it Replaced by Group Wheel

You aren't carrying forward your shell environment into the su adm session. so if you echo $PATH in the usracc account and the adm account, you'll find that they aren't equal (which is why adm can't find the updatedb command). All you need to do is tell su that you want to carry forward your env (su -m adm should do it) or just add the path to updatedb.

Though on my box updatedb is called /usr/libexec/locate.updatedb and is a script.

It sounds like your employer has disabled using sudo commands from any admin account, instead opting to include only specific users. This would mean only the employer's admin account would be able to use sudo. If you no longer have access to this account, you could boot into Single User Mode and run the visudo command to fix it. If they didn't remove the user from the sudoers list, you could also make a new admin account with the same shortname.