Was attempting just to get the OP on track with his question. Of course, reality can be very nuanced. Broker and exchange may invalidate or "forget" your stop loss for various reasons. Wether you get fill or not depends on order price and how long the order will live, after trigger has been triggered.
You can probably write entire books on the subject of various execution on exchanges. As it stands, very little one can do to protect against overnight gaps before the fact, unless one sells before that for some reason. Sometimes just not possible for trend trading when price gaps down hard right after a rally.
Yes. I should have been clearer in my first post. I meant stop limit order. Now I know that putting a stop limit order can turn out to be disastrous if the price opens gap down the next day (as per the example cited in my first post). Thanks once again for the clarification.