Is it usb mass storage that is causing the problem. Do people getting sd card problems use usb mass storage, I never use it and have never had disappearing media.

Also, it's possible to enable mtp mode which works well on windows but not so well on Linux.

Using apex launcher you can do:
long press home screen..shortcuts..Activities..Settings..USB computer connection (.UsbSettings)
Click on it and select Media device (MTP).

to do the same thing from the command line you can do:

setprop persist.sys.usb.config mtp,adb

MTP mode should export both the internal and external cards.

A reboot will give you back mass storage.