We still have maps of Tibet with the locations of said cities and more on them. Plus, we have had Rangers living in the region for countless years. Finding the cities or some trace of them would be a rather easy venture. Rangers would be deployed to sabotage the Qarir exploration covertly, while the Bloodsworn expedition would be prepared in the secret strongholds north of Tibet.
Rhûn, like the Bloodsworn, begins organizing expeditions to rediscover the lost cities. They are mostly made up of the troop types adopted into the Rhûnic army from the old Himalayan army, so they know parts of the land better. The expeditionary forces are ordered not to attack any natives unless in self defense. In the latter case, they are expected to take as many prisoners as possible. Messengers are sent to the Natural State to bargain for their cooperation.
One does not simply sabotage Qarir's expedition campaign. After hearing about the campaign, Krungor sends a large amount of skilled soldiers and explorers to help their campaign.
What I mean is, a ranger who ranges through Siberia is useless in Tibet or in the Sahara, the same way a desert or mountain ranger would be lost in Siberia. A ranger is only useful in a place he feels comfortable