A reboot shouldn't cause the loss of data. A reboot is just turning off and back on. If that is what happened I would suggest restarting it again and they may show. It happens.
Now if you are talking a reset, which means to erase data and problems and reset the device that is a whole other story. In that case, there is no guaranty that the files will be able to be retrieved, however it can't hurt to try.
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...