Me too. Since I got my sugars under proper control a few years back, I've lost pretty much all warning signs of an impending hypo. As a result I test my sugars 5 or 6 times a day to make sure I'm not heading over the edge.
My understanding is that we become desensitised to the effects of the hormone epinephrine (which is responsible for the tremors / sweat / pallour etc) if the difference between 'normal' blood sugar and hypogycemia is too small. This might be rectifiable, as you said, if you run your sugars a little higher for a while so that the epinephrine can start to warn you before the BS gets too low.
I haven't tried this myself though. Too proud of my A1c of 4.5!
All the best,