They haven't heard of it because it is far less common than the typical adult-onset type 2. The key: is the patient overweight or obese? It has been classically taught that 85% of type 2s are overweight/obese, thus many of the other 15% would be LADAs.
I have had a few adult onset so called type 2's patients, diet and med compliant that just seem to eventually need insulin for BG control. This article was the first I had read on the possibility of the auto immune theory becoming mainstream at least for some types of diabetes.