What happens when someone unblocks me?

I was blocked by someone yesterday while we were chatting. I knew immediately because all of a sudden, his profile picture went blank, his online and last seen timestamp disappeared, and my messages went one check only.

So I blocked him back at once. Today, I wanted to find out if he had unblocked me already. So I unblocked him first and went to his chat window, and saw his profile picture was back, and his last seen timestamp was an hour ago only.

Does this mean he has unblocked me already?

What are the signs to know when someone unblocks you?