Hi Scott,
Unfortunately if you have uninstalled LR as you've described (and might have ticked the options there for deleting all data, etc.) the InstallShield Wizard would have deleted your LR files permanently. These are not included in the diagnostic reports, so the only way to retrieve those Categories or Playlists is to re-import your backup *.cat or *.pl files (if you exported those before). Otherwise if you were not able to export your LR lessons before, you will need to re-do those particular Categories / Playlists / words -- if you've saved your personal media files (like recordings, pictures, or videos) in another location in your computer, then it will be easier to re-do things.
In another scenario, if you have simply deleted a word, Category, or Playlist in LR, there is a new function that works like your computer's Recycle Bin, so you can go there and "restore" previously deleted items. To do this, Go to the Advanced Play / Edit screen and toggle Playlists or Categories -- at the bottom of the list is a
Trash item. Select
Trash and you will see a list of previously deleted items that you can choose to restore or delete permanently.
Another new function is the
Backup / Restore Data in the Tools screen. This is different from the Import / Export Content function (available in the previous LR versions) as you can use this to backup everything in your LR (your database, or your database + media library) so you can easily restore your data when needed.
Sorry about what happened -- but just so you know, you can simply run the installer for any newer LR version without uninstalling the one you are currently using (since it works as an "upgrade" installation). In case you end up needing to uninstall, please do the necessary backups first so you can restore your backed up files after re-installing LR.
We are currently working on updating all the LR manuals and Support articles so we should be able to explain how all the new features work, but it will take a bit of time to finish everything. In the meantime, you can always ask here (as what you've been doing) and we will help you out!