No need to panic, right?

Ok so as if I'm not paranoid enough about my lack of preparedness for RVM, which is in 22 days. My HRM just went into complete meltdown last night.
I was late for my run, so I'm rushing around at home and I find my HRM is not picking up my heart rate, but I figure there is just interference. I get to the track and on my second warm up lap it just blinks twice and kaput. Nothing. Nada. Zippo.
I admit I didn't use the HRM to its fullest capabilities but in training I used it to make sure I was running fast enough on speed workouts and not too fast on LSDs. Now nothing. This is so not good.
Anyway, the run had to go on last night. So I did six warm up laps at a laughingly easy pace and then did 16x100-metre stride/100-jog and finished with six easy laps. I was supposed to be out an hour but I'd guess it was only 35 minutes. It was way too dark to continue.
The workout felt ok, though my hamstring tightened up on my final two 100-metre strides.