No I didn't

Why don't people take responsibility?

I just had to listen to a 15 minute conversation between my boss & the other person in my department.
"You didn't do this."
"Yes I did."
"No you didn't."
"Oh I must've done it this way."
"No you didn't."
"Oh then I probably did this."
"No."
"Well I'm sure I did this other thing."
"No you couldn't have. That's impossible."
and so on.

Instead of wasting everyone's time, she could have simply said "Oops I missed it. Sorry. I'll fix it right now." but she continued trying to convince the boss she had done something that she clearly had not. He wasn't even mad or anything, he was just leting her know she missed something.

I want my 15 minutes back that was stolen from me when I had to hear that nonsense.

UPDATE:I had to hear this same conversation AGAIN not an hour later.

Dense Dense Dense Dense