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 that 'may' be able to help you recover the data.
A few of the programs you could try would be... DiskDigger, MobiSaver, Android-Recovery and Tenorshare. They are all data recovery apps/programs. There are many others out there, so check around and see which you would rather try. There is also one called RECUVA, that I have heard is free, which you could try.
One important note though, most of these programs are not free. They may say they are "free" or have "Free Trials" and "Free Downloads". Yet to actually recover your data, and get your files back, you may be have to purchase the program/app. Just so you know.
NOTE: For future reference, I really would suggest backing up your data to a computer or cloud. Often. Better to spend the time doing that, rather than to be out all that stuff if the phone dies, things get deleted/erased or it gets stolen.