Why woud You do this?

It's a little lengthy but I could have help understanding it...
person A: yo you wanna goto the diner?
person B: yea
person A: alright I'll call person C

Person B overhears that person A will meet him downstairs
A and B leave the room without speaking
A goes to the bathroom and B is left not knowing what is
going on

person B calls A
person A: yo i'm downstairs
person B: okay i'll be right there

i just wanted the conversation interpreted

THAT IS HOW GENERATION x, y, z COMMUNICATE, THESE DAYS!

Just sounds like a breakdown in communication. Person B should have just stood downstairs and waited for Person A to come. If Person A didn't show up after 10 min, then Person B gives Person A a call and finds out what is going on. I hope Person B didn't leave the building after Person A TOLD Person B to meet him downstairs.

Why would who do what?

I presume A went to the bathroom because he had to go, and wanted to do it before going out to eat.

It seems B wasn't sure what happened to A and wasn't sure what was going on, or where they were to meet.

I gather they decided to go out for dinner because they were both hungry, and preferred eating together over eating out alone.

What is it you don't get?

Why would who do what?