Have you tried your DMM/Thermo-probe in a saucepan of rapidly boiling water? At sea level, you should read very close to 100C. Its a quick check that should highlight any potential problems....
Regarding your roast, theres a good chance that it may not have even reached First Crack due to the low DMM reading. If this is the case, theres probably not much hope for the Bugisu unfortunately. Give em a go after a few days rest and see how you go... might be lucky :-?