Installing plugins and themes doesn't work the same on heroku as it does on other servers. You can't just use the ACP to install them because of the way heroku resets. Instead you must install the plugins and themes before pushing the code up to heroku.
This is why it shows that your theme is activated. The database is persisted across resets of your heroku server. But since the built assets directory in the git repository were created under persona, it resets to that.