Two of my cats also meow more when they can't see me.
Mitzi meows when she is shut away, which happens regularly beause she is always going into sheds, wardrobes, cupboards. That's a proper yell 'come and get me out'.
Blackie sits on the stairs and meows untril one of us goes to see what is wrong. She then looks smug.
Both Mitzi and Blackie have some Siamese in them (Mitzi is half Siamese) and are therefore prety vocal.
Mini rarely makes a sound, just a small mew when she realises she is going to get her favourite dinner.
Flynn is an Egyptian Mau and therefore has an wonderful repertoire of cute chirps and whistles, but he does not meow.
They all purr
.