Try restarting the phone and see if they show up. Sometimes you have to restart (turn it off and back on) to get all the files to show.
Should that not work, check your google account to see if they are in fact in there. If they aren't, and you reset the device, then it depends on what reset you did on 'if' you can 'maybe' get them back. If you chose a "Factory Reset" and opted to keep your data, then the information I am including below may help get the data from the device. However, if you chose to do a full on "Hard Reset" and wipe everything on the phone and start over, then anything on the device is gone.
While there is no guaranty that you can get them back. Deleted does mean deleted. There are a few apps/programs out there...