Aren't we all adults here?

This is the question I asked myself after my most recent conversation with my boss. See first about a half hour before I was leaving for the day she asks me if I'm working tomorrow because she needs to talk to me about something. I do work is what I tell her then I ask what she wants to talk to me about because why would it need to wait until tomorrow. Then I say are you going to yell at me (not that she yells just mean did I do something wrong). She says sort of, and I just want to make sure I give us enough time to talk about it.
Ok seriously who the fuck does that. I mean if you have something to say just say it. Don't tell me about it, then not tell me. So I was like just tell me what you need to talk to me about. To which we kind of get into it. I think its stupid that she won't tell me, and she's like well you didn't need to ask if you were in trouble. Really I was super irritated at this point. It just doesn't make sense to make me think about it all night till I work again. Who wants to go to working thinking they are going to get yelled at without knowing what its about. So I go talk to another co-worker about it. You know just to make sure I'm not the one being unreasonable by thinking that what she had just done was bullshit. The co-worker totally thought it was crap too. Because like I said seriously who does that.
Anyways after about fifteen minutes my said boss comes back and says we can just talk about it so you don't have to stew about it all night. Thanks for understand you were being a retarded bitch I think. So we go down to the office, and she shuts the door, which for the record is never a good sign. Then she tells me an associate came to another manger and our HR manger and told them that I had said "let get the fuck out of here" one night while closing. Now I'm trying to hold back my laugher here and take seriously what is absolutely ridiculous. I do not remember saying this, but clearly if you made it to line to of even this post you can see that I might have a bit of a potty mouth.
Then my boss proceeds explain that she was doing me a favor (my words not hers) by just nipping the situation in the bud so to speak, and that it could have turned into a whole big thing. Meaning that they could have investigated, asking more people if they heard me say it etc. etc. etc. I'm sitting there trying to take this all in without saying back are you fucking kidding me. Which I'm proud to say I didn't do, but come on I work retail I don't teach children. I'm wanted to dare her to investigate something so ridiculous considering the fact that half the building has a much worse mouth than I do. Some of those above me the worst offenders. Its not like I swore at someone, and yes I have heard other managers actually swear at associates. Yet I'm the one being accused of being unprofessional. Trust me when I say if I had to make a list here of all the unprofessional things the people I work with have done I would be here till next year. Including the fact that the she said it in such a way as to make it a threat, which breaks company policy far worse than my "lets get the fuck out of here."
I just don't get it honestly. Everyone I work with is over the age of 18. Swearing though not professional is part of every environment. Get the fuck over it. Its not like there were customers in the building, or I was yelling at someone. The best part is that I was telling the story to my HR manger, and she laughed her ass off because what I was told was not even what happened. Its completely ridiculous. Seriously if we could all just focus on real problems we all might actually get some fucking work done.