Yeah, weird that I can't find them either. The short answer is: if you attack while hidden, you have advantage on the attack roll. After the attack succeeds or fails, you are no longer hidden.
The long answer is more complicated and it's something I want to revist. To start with, here are the RAW rules:
[ +- ] RAW Hiding Rules: D&D Basic Rules p. 60
Hiding
When you try to hide, make a Dexterity (Stealth) check. Until you are discovered or you stop hiding, that check’s total is contested by the Wisdom (Perception) check of any creature that actively searches for signs of your presence. You can’t hide from a creature that can see you, and if you make noise (such as shouting a warning or knocking over a vase), you give away your position. An invisible creature can’t be seen, so it can always try to hide. Signs of its passage might still be noticed, however, and it still has to stay quiet. In combat, most creatures stay alert for signs of danger all around, so if you come out of hiding and approach a creature, it usually sees you. However, under certain circumstances, the Dungeon Master might allow you to stay hidden as you approach a creature that is distracted, allowing you to gain advantage on an attack before you are seen.
Passive Perception. When you hide, there’s a chance someone will notice you even if they aren’t searching. To determine whether such a creature notices you, the DM compares your Dexterity (Stealth) check with that creature’s passive Wisdom (Perception) score, which equals 10 + the creature’s Wisdom modifier, as well as any other bonuses or penalties. If the creature has advantage, add 5. For disadvantage, subtract 5.
What Can You See? One of the main factors in determining whether you can find a hidden creature or object is how well you can see in an area, which might be lightly or heavily obscured.
There is also a
great Sage Advice segment from Jeremy Crawford on the Dragon Talk Podcast where the man who wrote the rules discusses how they work and why he chose to make them work that way. I love listening to JC talk game design.
In our game, I have broken RAW to allow for hiding in combat even when not definitely behind total cover or heavily obscured. With doing combat in the theatre of the mind, it is hard for players to know for sure if their characters are unseen without asking. And, because "asking the DM" can take a day or more in PbP, I decided to share the responsibility of deciding whether your character was seen with you, the players, through the "Battlefield Features" or "Interesting Features" mechanic (I should standardize the terminology).
I suppose this is like creating customizable zones that a player can define as "heavily obscured" with a good enough narrative. A player invokes Batlefield Features (like "Dense jungle foliage" or "Waist-deep bloody water") narratively to gain a one-time bonus for creative or cinematic descriptions. Although I technically arbitrate whether the attempt was successful, that's mostly just a technicality to prevent people from abusing it. Mostly gives players the freedom to do the cool things their character is meant to do. The party's rogues have used these features well to hide, giving them sneak attacks and gain advantage on attacks.
I will take this opportunity to remind everyone that the Battlefield Features are meant to grant a one-time bonus. For example, you can hide in the "Dense jungle foliage" once with full support from me, but if you do it every round then I will probably say the monsters are getting wise to your shenanigans and you cannot attempt to hide there anymore. Then again, I might not say that. I remember when I witnessed MoMo's crocodile-like tactics in the bloody water of the Shambling Mound encounter and it was just so fucking cool that I didn't once say no to Ygne's attempts to hide because they were so cinematically awesome.
Ultimately, my system is no more dependent on petitioning the DM than the RAW rules, but it does give you the context and freedom to try things that make sense to the scene. It works as smoothly as it has so far because you, the players, aren't trying to abuse it and have a great sense of cinematics.
Does that help?
