The OP doesnt say that the Paynim have come to look for anything so Im confused as to why they are trying to locate hidden at all. What makes them think there is something to find?
Even if theyre just cautious and scanning the area then thats a ‘passive perception’ type thing to notice if something is unusual - if they do notice, then you have your location for a locate hidden spell to scan.
Because it's around 30 years ago that this episode of play occurred, I don't remember the details. Rather than Detect Magic, relevant magic could have been Detect Life or Locate Object (the PCs may have been carrying some sort of Baklun relic) or one of the various Detect Thought-type effects that RM Mentalists get.
If the PCs weren't hidden you'd have to determine the nomads' location, right? Place them down relative to each other and then determine how the nomads move based upon the PCs' actions?
So what's stopping you from placing them down without them knowing where the PCs are? Determining how they move in the absence of PCs' actions? That gets you their location for the Locate Hidden check.
Why would you need to draw up a tactical map? The check as described depends upon range, not precise positioning. The only question that needs to be answered before rolling it is "how close do the nomads come to the PCs?" No need for a tactical map to determine that.
I don't quite follow your contrast between "placing them down" and "tactical map". But in any event, while it's correct that an overt encounter gives rise to some of the same problems, it's much easier in that case to treat each group of characters as a reference point both for character motivation and for character positioning - eg "the nomads surround you on their horses, well within bowshot range". This is a thing the nomads might sensibly do, and also establishes ranges for subsequent resolution.
Now if the PCs try to escape being encircled - eg by running into the foothills - it is once again the case that RM has no very satisfactory means for resolving this (the Move/Manoeuvre table is really intended to be used for single bursts of movement, rather than chase-and-pursuit). I only remember one chase and pursuit episode from mid-ish level RM, and that was resolved predominantly by GM fiat - I could easily have presented it as another example of granular resolution based on setting => situation not working. At the levels where the episode in the OP came up, escape would always have been by way of teleport or perhaps flight and so the issue of pursuit would normally not arise.
Are you suggesting the situation can't be granularly characterized because the PCs are static and the NPCs aren't? That's just not correct. You can make decisions for the NPCs, and it's pretty standard procedure to do so.
Once you've established what they want and what they can do, how is the process of their resolution any different than if they were PCs, outside of who's playing them?
Establishing
what they want is already a complex task in a
setting => situation approach. Because of "who's playing them", questions of adversarialism, or what it is fair to suppose that a group of dozens or hundreds of nomads might have learned from (eg) Dream spells and Guess spells and whatever else is conceivably going on in the fiction, are highly relevant. The contrast here is with
@AbdulAlhazred's examples of Dungeon World resolution, where
what they want can be established, in part at least, as a consequence of resolution rather than an input into it.
And even once that is resolved, there is then the question of establishing
what they do and
where they do it, in a case where I - the player of them - know what they
should be doing and where they
should be doing it. If I was a player in that context, having learned the location of the treasure by reading ahead in the module, I'd be a cheater!
How many people are searching, in which areas, etc? I agree, you can make up your own procedures. I think that's the point, the sorts of high granularity 'sim' type rules that a game like RM uses don't work here. Even if you hack them enough to get some kind of results there's no guarantee it's fun, and I would argue that so many of the inputs are decided on the fly by the GM that this process is indistinguishable from just making up the answer. At best I can't see how it is superior to a DW move.
All this exactly.