Amazing to hear about your clever dogs, my sheep have similar skills, and my cats used to know when I was sick, sadly passed away now. Yes it's quite possible to go hypo without knowing. I once experienced no symptoms except realising my actions were nonsensical, i.e. running a bath, putting on my coat to go out, then trying to make a phone call..., and then suddenly realising my actions were crazy! When I checked my blood sugar it was 1.9mmol! I couldn't believe it, I double checked on another meter, yes 1.9mmol. In this case I believe it was because it had reached this level very slowly giving my body a chance to adapt, until it reached a critical level. Soon after taking the reading in fact, I did get all the classical symptoms: sweating, shaking. The speed and relative change in blood sugar levels effects presentation. Autonomic neuropathy can also cause non recognition of hypoglycemia.