How does monster hiding work when some players detect them and some don't?

Question

In one of our battles in DnD Next, I had some bugbears hiding in trees trying to attack the players.

The bugbear rolled a 21 on its attempt to hide. Four of the players rolled less than 21 on their wisdom, but one character rolled a 22.

The bugbear has a "bushwhack" attack, which does an extra 2d6 damage to characters from which it is hidden.

This question has three parts:

1. Since the character who saw the bugbear hide declared to the group that the bugbear hid in the trees, does that mean that everyone now knows where the bugbear is?
2. Does the bushwhack damage apply to any of the characters?
3. Can the Bugbear know which PC not to attack, because it knows that he was spotted (the character shouted it out) vs. the other PCs from whom it is supposedly hidden?

In general, how does this work?

Answer 1

Obviously since there's only 31 pages of D&D Next rules, these are the kinds of interpretations that have to be informed by earlier editions and DM fiat.

1. Usually "there's a bugbear in the trees" is not sufficient to avoid a sneak attack because the others still don't know exactly where it is. It certainly might allow them a second Wisdom check to spot it if he's pointing over in the general direction, perhaps even with Advantage if he can be a little more specific (and take an action to point it out).

2. The bushwhack damage would apply to anyone that hasn't spotted the bugbear by the time it attacks. Notice the power doesn't' say "unaware of his existence," it says "hidden from them."

3. In terms of who spotted him, I would say it depends how obvious the PC is being. If he spots the bugbear but keeps his peace, then the bugbear might mistakenly attack him and get more than he planned for - but if he's yelling "there's a bugbear!" and gesticulating in his direction, then no duh he knows that guy saw him.

5e is going back in the direction of earlier editions, where "the DM makes a ruling that seems like it makes sense in the game world" is always the correct answer, and there will not always be rules to cover every edge case.