Otherwise a pretty snazzy app; I had an issue lately where I was missing the photos taken with Nokia Camera after a soft-reset, which got me fishing around for solutions.
It turns out the solution is within the app. From Nokia Camera. Open Settings. Under Pictures, scroll all the way to bottom and there is an option for restoring your missing photos. “Find photos and videos shot with Nokia Camera”. Click on it and Wait for it to finish. For best result, don’t get out of the app. Let it restore completely. It may take a while depending on how many photos you were missing.