Harvery, steps you mentioned are cent per cent right. Have you tried purging cache? also, delete the cache of the browser as sometimes browser's offline cache over rides the fresh content.
for clearning theme cache's you can go to (in your moodle site, not CPanel)
Administration > Appearence > Themes > Themes Selector
and on top you'll see button "Clear Theme Cache"

alternatively, you can go into
Administration > Development > Purge All Caches

and in the end, do delete cache of your browser as well.
though I have just tested it myself @ lockquiz.com/education and it still is showing the moodle logo. in case if this doesnt work, let me have access to your CPanel and Moodle plus your logo, and I will do it for you.

