Lama Ole’s answer:
If you dream of me, then your virtue is gone! No but seriously, one can say that the teacher is the direct gateway to our own buddha nature. The teacher is actually the mirror showing us our own face.
So if you dream of buddha forms, hear mantras, or see your lama, then this actually means that you have direct access to your own buddha nature. This is very good! It means that the veils of dust on the mind are quite thin and that the timeless nature of mind is close to breaking through. Another positive aspect of dreaming of the teacher is that if one dies and doesn’t have Phowa, then one has a very good chance of seeing the teacher shortly after death or while dying.