You might want to ask this same question to the main GT-10B thread: http://www.talkbass.com/forum/f36/bo...art-2-a-837373
I understand the deal about putting a lot of time into patches, especially if you can't recover them in a situation like this. This is almost enough to make me not only back them up via USB but to write everything down!
You can get to the LCD contrast blindly by powering up, pressing the System button, pressing the right-hand button on the dial 8x, pressing Enter, then turning the dial hard to the left to get maximum contrast, then pressing Exit 2x.
If that doesn't work and you resort to doing a factory reset, you can do it blindly by powering up again, pressing the System button, pressing the right-hand button on the dial 13x, then pressing Enter 2x.