Have you calibrated your refractometer in plain water? Mine reads 0.2 Brix low. Yours might be even farther off, and values need correction if that's the case.
I seriously doubt any beer would finish below 1.000 unless you used like 30% or more of simple sugars to dry it out, then maybe it's possible.
My guess is your final Brix reading was a little lower than reality. As @sneezles61 mentioned above, using a hydrometer is the only way to know for sure.