supermount-1.2.7a doesn't notice when an USB flash
drive is disconnected, changed elsewhere and then
brought back. In this case filesystem isn't actually
re-read, thus one can't see new files etc etc.
As a solution one may set up hotplug's event scripts (I
have such one in /etc/hotplug/usb.agent), that will
force supermount's umount for such device via SM /proc