Give up on thumb drive
The TrueCrypt drive that I setup on a thumb drive had file corruption problem. Luckily, I have a backup at another location. But that is the last warning sign to remind me that I should stop using it to store important data.
In fact, after tons and tons of data lost on thumbdrive, I am pretty decided that I will not use thumb drive to store any important data any more. It will be still a mechansim for transfering data from one machine to another machine when network is not available. But That's pretty much it.
From now on, I will stick to USB 3.0 harddisk. And even with that I'll make sure that I have backup on everything.