Sometimes files might get accidentally deleted from a personal or shared Dropbox folder. You can restore any file for 30 days (as of November 2015).

1. Go to the Dropbox Website and login
2. Click on 'Deleted Files' on the left, or the Trashcan icon near the top
3. Hover over the item you wish to restore and click 'Restore'

https://www.dropbox.com/en/help/296