Ummm... Microlensing is one of the most advanced methods humans have in the year 2022. Surely we'll have waaay more advanced methods in the year 1,000,000 AD, as do, presumably, the more advance and dangerous aliens have right now. To suppose they are still using ancient techniques to look for us, is equivalent to supposing they are still riding around in horse and buggies. It's crazy, wishful thinking, at best. IMHO
Microlensing or what if we are them that we are seeking one never knows.