Their bodies are invisible to the naked eye (or at least, the naked human eye), though this Forma's invisible arms do block part of her clothing from view at this angle.
Experts are unsure whether this counts as having a face or not having one. To try to put the issue to rest, those experts tried to ask Bats to find out if they detected a face (or a lack of a face) with echolocation. Unfortunately, when the experts attempted to make this request, the Bats just went "!", flew at them, and spammed Strike and Bite- not an ideal response. The experts are fine now, and they're considering asking the recently-discovered Gem Bats instead. Hopefully those are more amicable.