Hello, I have a fix for this problem after having posted it for a differently branded stick, but with the same prolific controller on bugzilla.
See bugzilla #11640
Whenever you create multiple partitions or a non fat(32) file system in a partition on the stick the inquiry of the stick timeouts. The default linux timeout is set for 5 secs, and the stick takes 14.5 seconds. So if you set the timeout to 15 seconds or more, and reinsert the stick, the stick should be mountable and readable. Just remember to add this to your boot scripts, or repeat it every time you reboot the kernel.
The inquiry timeout can be set to 15 sec with the following command line:
echo 15 >/sys/module/scsi_mod/parameters/inq_timeout
Or if you prefer the grub command line is :
I hope this longer timeout will someday be standard for the kernel. Or maybe part of an exception list when a prolific 2528 stick is detected.