Dropbox only keeps history for 30 days by default. The exception to this is if you have either Dropbox for Business or if you have Extended Version History in Dropbox Pro. The latter allows you to restore to a previous version of anything changed within the last 12 months, or if you were a member before November 2014 then you can restore to any point in time, just like Dropbox for Business.
As you have deleted from Fedora within the Dropbox directory, Dropbox has synced the cloud version of your files to the deleted state, and now when you've booted Ubuntu and the Dropbox daemon has ran, it has now synced that machine to the deleted state.
I see there are two options for you:
- You could try a restore from the filesystem using a tool such as extundelete. You can try this on both your Ubuntu and Fedora systems as they both carried the files.
- You could contact Dropbox support and see if there is any chance of them restoring the data. It may be hanging around on their systems somewhere waiting to be purged, so there is a small chance they could recover it. Don't hold your breath though. See their guide My files are missing. How do I get them back?.