So this morning I learned something about Basecamp that I'm betting most users don't realize: your database probably isn't getting backed up.
I use a back scheme that includes the My Documents folder, but I never in a million years thought to back up c:\users\<my username>\AppData\Roaming\Garmin\Basecamp\Database\4.3 which is where Basecamp stores it's data.
Now I did make explicit backups from time-to-time, copying the database to an external hard drive. But this scheme relies on my explicitly making copies of my database.
To move your database to someplace that actually makes sense and will be picked up your typical back scheme:
1. Make a backup of your database in a place that makes sense (i.e. My Documents\Garmin Backups) File -> Backup ...
2. Select Edit -> Options -> General, Database Options and move your database location to some place that is backed up as part of your daily scheme
3. Restore your back up into the new database
And, ah, Garmin: This is a ridiculous place to store user data! (yes, I know other software does it too, but it doesn't mean it's a user-friendly practice).