As far as I know, if you don't know where it is, just 'locate locatedb' if it's called that on your system. Then ls -al the file. It's timestamp should show when it was updated.
And, depending on the setup, it'll warn you if you use the command and the db's more than a week old, so it's not usually anything to worry about. And it often is scheduled as a cron job to be updated every night.
Could be wrong about all this, but I think that's it. *g*