I've been a type 1 diabetic for 36 years and know what you're dealing with. Fortunately (or unfortunately, depending on how you look at it!), my wife tends to notice my lows before me when they occur. This inattention often comes from having become "used to" those events and losing a bit of sensitivity. If one passes out, they
can regain consciousness and be able to handle their situation, but one should never expect that to occur. This is the benefit of tightly monitoring your health when you are alone.
I'm going to make a few suggestions:
Perhaps you can come to an agreement with him that when he feels sweaty or otherwise abnormal he'll agree to test his sugar, no matter what.
If the problem is taking too much insulin before meals, take less (especially when dining out) than he feels he needs and then test an hour after and make adjustments from there. If he carb-counts, he may get good at judging, but it still takes a lot of guesswork and needs to be constantly tested to assure correct carbs to insulin matches.
Coming off of not having his basal insulin for an extended period, he is quite likely having trouble re-regulating his balance between the two. Although it might be an isolated incident, he should never go without one, but rather go to another pharmacy and get what his body requires.
If his lows are during the night, I would suggest that he set the alarm for a week to between 2-4 am (depending on when he eats last at night) and test his numbers then. This way he will get a better idea of how his body trends at what seems to be the incident time. If he remains low, he should cut back on his fast acting insulin one unit at a time until he gets the correct balance; if they are very low he might cut back two.
If his numbers are low at all pre-meal times, he needs to cut back on the basal dosage. Either situation should be cured by doing this.
Get a good doctor. The Joslin Center for Diabetes in Boston is one of the top diabetes research hospitals in the country, and has many affiliates throughout the US; check and see if there is one near him. It pays to be treated by the best in the field. Go to their web site, they also have a bookstore with titles about many topics that are very helpful to regulating his condition.
Lastly, the hardest part, try not to worry.