It's a little like getting a phone call from a guy claiming to be a Nigerian prince.;-)
You wrote, "The thing about being contacted by angels is how do you know they are angels? Perhaps they aren't angels at all but just pretending to be. Perhaps they are demons...or just aliens."
Interestingly, that is the assertion of Islam that ole Mo got his messages from -- insert noun of choice here -- in a cave. As Wiki blandly states, "Muhammad's first revelation was an event described in Islamic tradition as taking place in 610 CE, during which the Islamic prophet Muhammad was visited by the angel Jibril (Gabriel), who revealed to him the beginnings of what would later become the Qur'an. The event took place in a cave called Hira, located on the mountain Jabal An-Nour near Mecca."
Source: https://en.wikipedia.org/wiki/Muhammad%27s_first_revelation
So some argue angel. Other argue demon. Alien might be an interesting supposition. After all Jibrīl is described in some parts of the whole as having six hundred wings. Maybe they were other kinds of alien appendage? But also "in the form of a man with feet astride the horizon." Big alien? Big demon? Big UAF?
“The thing about being contacted by angels is how do you know they are angels? Perhaps they aren’t angels at all but just pretending to be. Perhaps they are demons...or just aliens.”
I suppose it would depend wholly on what your own perspective would be.