On a Mac, if you configure SuperContainer to store images in a mounted volume, and one day it mysteriously stops seeing all the files it had previously created, but otherwise seems to be working normal, there’s a good chance that someone tried to operate it while the volume was not mounted.
What SC does if you give it a path that doesn’t exist, is it makes that path for you. This is a useful feature in most cases, but if the volume you are targeting is not mounted (on a Mac), SuperContainer will make a directory with the same name as the volume in /Volumes. Then next time the volume actually is mounted, the sym link in /Volumes gets a 1 appended to it.
Fortunately this is exceedingly simple to fix. Mount the volume, copy any files that were uploaded into the impostor folder to the proper location in the volume, unmount the volume, delete the folder and remount the volume. Done.
PS: Thanks to Val at 360works for the tip.