Is it possible for my husband not to know he can even message on PS4 when he clearly has been added to group parties and a girl messaged him in their own chat?

I accidently saw a message saying, Hey there :), from a girl on PS4. When I asked my husband about it, he told me he has no idea what I'm talking about and also told me he had no idea he even could message people. He also said he sets himself to appear offline. Well... from what I saw he was in groups with 50+ people and then a private one with a girl. I couldn't see messages back and forth. He plays ALL THE time when he's off work and sometimes stays up until 6am doing so..he also does game fly. So anyways...Do I believe him or is something fishy going on? I have no idea about PS4 except Netflix and Hulu.