person A: I can't believe I walked in on someone using the restroom. 
person B: Oh my_comma_ that must've been an embarrassing situation!
person A: It was! I knocked first and no one answered_comma_ so I thought it was okay to go in. 
person B: That's ok_comma_ you did the right thing. It probably happens to lots of people.
person A: Thanks_comma_ I'm sure it does haha