Sometimes memory stick dies. This is how to bring it back to life.
1. Check the partition table, to get the impression of the way Linux recognises memory stick as a device.
# cat /proc/partitions major minor #blocks name 8 0 39070080 sda 8 1 22528296 sda1 8 2 971932 sda2 8 3 15566985 sda3 8 16 976384 sdb 8 17 971901 sdb1