Oops

ㅠㅠ Has anyone else ever had an experience where they feel they may have misrepresented themselves without even knowing due to wrong timing and/or playfulness?

A friend and I were walking down the street today and we had just been talking about how her applications for jobs after she graduates is not going so well so I was trying to cheer her up. She asked if I could help proofread her English résumé  and I was like of course. Then she asked a professional way of saying I've added my résumé to this email so please check it. So I said, 'Attached to this email is a copy of my résumé. Have a look and get back to me.' But she was looking gloomy as she noted it down on her phone so I decided to make her laugh. I repeated 'Attached to this email is a copy of my résumé. Have a look and get back to me, motherf**kers.' But just then, the couple in front of us kissed and not wanting to lose the moment I said in a sheepish voice, 'Get a room' (as you do 😩). Normally the reaction I get is the couple turn and smile a little embarrassed or giggling and we all laugh. But nope, the guy turned and said 'Hey, I heard what you said.' I really thought nothing of it and smiled at him and continued walking. I must have forgotten I'm in Korea. A few steps later my friend said 'You shouldn't have said that.' So I was like come on, that's a silly joke we all throw around, I meant no harm. But after my a while I asked her why she thought that was rude. She said, it wasn't even so much the 'get a room' but the swear word I used. She thought that the 'mofo' I said was for them and suddenly, I felt bad. This couple I don't know probably think I'm swearing at them for no reason whatsoever and I even smiled like an idiot about it. Not only that but I feel like 'get a room' in a conservative country isn't a funny joke even if the younger ones say it all the time. Saying hello to a stranger gets you a scared or weird look, let alone cracking unexpected jokes. I wish I could reverse and explain and apologise or not say it at all.