A bored party with little of their own initiatve seeks quests from a high level mage NPC, who spends most of his time in his remote mountain tower. The yellow exclamation mark over his head foretells the banality of his task: "I require the feathers of a Hippogriff to complete my scroll of fly!".
"You got it" the adventurers say "where can we find some hippogriffs?"
"Eh....." the Wizened mage freezes in place as the DM loading screen comes up. The Judge hastily rolls several dozen times to find a lair of hippogriffs: first they roll to see how many lairs dwell within these wild mountains, and then rolls to see if any have a hippogriff. Tragically, a roll of 8 on 1d8 follow by only a 7 on 1d12 yields a Hippogriff. Assuming a % in lair roll is not needed (We're already rolling for the contents of a lair, after all), this still leaves a 1 in 96 chance that any given mountain lair is a Hippogriffs. Surely, there must be a better way?
Well, it just so happens that 1 in 96 is remarkably close to 1 in 100, and rolling 1d100 should give a similar outcome to which numbered lair would be the first to be of Hippogriffs. Let's take this a step further, for ease of example, and note that there are 2d4 lairs in a wilderness mountain hex. At an average of 5, one could argue that the 1d20th closest mountain hex should contain the closest Hippogriff lair.
The Judge rolls 1d20 and gets an 8. They count out the 6 wilderness mountain hexes immediately surrounding the mage's sanctum, then 2 more in the 2nd ring of hexes. "Yes, yes" the grouchy magic user finally says "I've watch their flight patterns from my observatory. Their nest can't be more than 12 miles directly northeast from here", and the party sets off to investigate that hex, with the Judge using whatever method described in ACKs: Lairs & Encounters they best prefer to handle searching for the lair, the contents of one having already been pre-determined.
So... is there something I missed or does this roughly work? Is it an idea that could be more generalized to account for different terrain types and different probabilities of success? Would it stand to reason that Mayors and Town guards would be vaguely aware of the closest brigand lair or orcish camp? Are there other factors that need to be considered? What's the best way to handle lair amounts like 1d3-1?