I'll beat it was pretty scarry finding your rear brake not working!
Several years ago, I raced an ISDE qualifier, and day one took 9 hours (day 2 was better, and only took 8 hours). About 6 hours into the event, I had used my rear brake soooooo much, I boiled out all of the fluid, and lost the rear brake. While I should have just quit, I elected to continue, and landed on my head a couple of times when I headed down a steep hill, not remembering my rear brake was gone. I now carry a little bottle of brake fluid in my fanny back for these type events. I used an old eye drop bottle, and just cleaned it good. My thought here is that I could have gone faster had I just taken the time to add some fluid. Would have had to pump the brake to make it work, but better than no brake at all.
I use the same stategy with the clutch and brake levers, and carry an extra just in case. The two minutes it takes to change, is easy to make up at the faster race speed.
At any rate, kind of sucks that you had the problem, but these things happen.
Rick