The game is also about the world the PCs inhabit, and that world goes on without them if they aren't there...or if they are there and do nothing.Yeah, I don't understand the whole fascination that some people have with applying rules that are meant to produce narrative and explore fiction when applied by PCs being applied AT ALL by NPCs. I honestly confess, even in my early days as a GM I never did that or thought it would be a good idea. So, I wouldn't consider that kind of thing as a very good option, myself. The game is about the PCs and the players telling me what they do, etc.
Shouldn't there still be a chance, though, that if the PCs do nothing except stay quiet the riders will miss them and just move on?Right, which is why I posit that something has to happen, the players have to do something, or encounter some consequence that will move the situation along at some point. Now in Dungeon World the GM can simply make a move if the players essentially 'forfeit' theirs, and this is an explicitly described situation. It COULD also fall under 'Golden Opportunity', which is a rule where if a player describes a course of action which clearly ignores potential danger, then the GM is free to bring it down on them even if they DO describe some other unrelated action.
This assumes the dragon a) sees me, b) happens to be hungry at the moment, and c) doesn't have something more important to do; and while all three of these are fairly likely, none are outright guaranteed.Like if I tell you a dragon is flying your way and you then describe to me how you unroll your picnic blanket, guess who's going to show up for tea?!
Having the Paynims camp nearby is one of many possible random outcomes should they not initially notice the PCs' presence (or - even better - maybe they did notice and are faking that they didn't while a few go for reinforcements; "making camp" nearby is just their excuse to stay in the area and keep an eye on things).Bringing it back to this case, I think I suggested maybe just having the Paynims camp nearby might be a fairly neutral 'soft move' kind of action. I'd consider this if the PCs simply don't do anything. Now they can either try to keep digging discretely, try to leave unobserved, or whatever. It has the virtue of leaving things at a relatively low level of tension, providing plenty of room to ramp things up again. It would be a pacing thing though. If things need to be kicked up a notch, just have them find the PCs, that's a PERFECTLY legitimate move!