Hello,
Investigating your report we've found a bug in the Base Setup code. "Rebuild modules database" button doesn't work properly when in Advanced View. I have fixed the issue and it will be included in the next release.
In the meantime, I can suggest you to switch to "Simple View" and click "Rebuild modules database" from there, it should be working properly that way. You should see a new package "Uncategorized" and in its "Optionals" you'll find your module. If needed, you can also use Advanced View from that point as well. If you need to rebuild modules database later again, make sure you're triggering it from Simple View.
I apologize for the inconvenience caused and also thank you for this report.
Kind regards,
Arek