I have not, but I've been around people who have for any number of reasons, including low energy from lack of food, overexertion, locking knees while standing around, seizures, and idiopathic reasons (which is the doc's sly way of saying, "I dunno").
Two memorable times. Standing in formation for a long time in the heat. Thud. Thud. Thud. And so on. We probably had about eight or ten who hit the deck. It was almost like there was some suggestion involved after the first one went.
Second memorable time, lady in the office said she was feeling faint. She went to the in-office bathroom just to run some water and splash it on her, and another office lady suggested I go there in case she had problems. I was standing behind her at the sink, talking to her, and she said, "I think I'm going to faint," and then just slumped. She wasn't heavyset by any means, in fact had a nice figure, but she was about my height and big-boned, and dead weight at that point. I grabbed her under her arms to keep her from hitting her head on the sink, but she just kept slipping down, fast. The best leverage for rescuing her was to wrap up around her chest and lower her away from the sink, but I was way too inhibited for that, so I ended up with my forearms in my best vise grip around her upper ribs (ended up bruising them), and put her down gently on the floor.
After she revived and we all got back on our virtual or literal feet, I was relating the event and my issues of the instant, and she said, "If you'd grabbed me around the chest, I wouldn't have known it. And now my ribs hurt. If there's a next time, just do what you have to do."
So what were we talking about? Oh, yeah. Lina, I think it's a good idea to get checked out, because you never know, but most of the fainting spells I've seen have been for pretty innocuous reasons. I wouldn't worry majorly unless it happens again, and please, do think about a doctor's appointment in the meantime.