A few times that I can think of off the top of my head.
Years ago, a friend who had passed. I dreamt that I picked him up hitchhiking. I had even told him that I'd thought he was dead, then he got a little see through in the dream & admitted he was. It was a very vivid, bizarre conversation that has stuck with me forever.
At least twice since my dad passed. Those dreams usually start to dissolve when I remember he's dead.
And more recently, I dreamt of his mother, who died when I was a kid. It was so real, when I woke up I initially planned to visit her to talk about my dad...weird...
I get what you mean about not knowing the real from the dream when you first wake up.
Honestly? I think it speaks to an emotional need so strong to see the person again, our mind does it's best to make that happen.