I have noticed this problem across all distros including Kubuntu and openSUSE. Many times my Nikon D 7000 and Canon HF 11 are not seen or mounted by Dolphin. When I connect the Cameras I don't get any notification in the tray which otherwise shows connected device. Ironically when I open Nautilus then I can clearly see the cameras mounted.
I also have a request that what these devices don't appear on Dolphin's side panel automatically. It makes life easier for a users.