Jimlock
Adventurer
Ok, so Rope trick says:
...and Discern Location says:
Without a doubt, Discern Location can find someone hidden in a Rope Trick.
Rope Trick specifies that it DOES NOT protect against divinations that work across planes, and Discern Location DOES work across planes. Moreover, Discern Location clarifies that only mind blank can stop it.
So lets assume that Salamar (Wizard#1) is in room number-5 of the "Inn of the Dripping Dagger", in the Trades Ward, in WaterDeep.
Thelmaren (Wizard#2) is somewhere in Cormyr (where exactly is of no importance).
1-Thelmaren casts Discern Location to find Salamar. Without a problem, Thelmaren finds that Salamar is on the Material Plane, on Toril, in Faerun, in The North, in Waterdeep, in the Trades Ward, in the Inn of the Dripping Dagger, in room number-5. Case Closed
2-Salamar is in room number-5 etc etc... and he casts Rope Trick. Once again Thelmaren casts Discern Location. Now all Thelmaren knows is that Salamar is in an extradimensional space that is outside the multiverse of extradimensional spaces (“planes”).
Rope Trick Wins. Case Closed
The upper end is, in fact, fastened to an extradimensional space that is outside the multiverse of extradimensional spaces (“planes”). Creatures in the extradimensional space are hidden, beyond the reach of spells (including divinations), unless those spells work across planes.
...and Discern Location says:
Nothing short of a mind blank spell or the direct intervention of a deity keeps you from learning the exact location of a single individual or object. Discern location circumvents normal means of protection from scrying or location. The spell reveals the name of the creature or object’s location (place, name, business name, building name, or the like), community, county (or similar political division), country, continent, and the plane of existence where the target lies.
Without a doubt, Discern Location can find someone hidden in a Rope Trick.
Rope Trick specifies that it DOES NOT protect against divinations that work across planes, and Discern Location DOES work across planes. Moreover, Discern Location clarifies that only mind blank can stop it.
So lets assume that Salamar (Wizard#1) is in room number-5 of the "Inn of the Dripping Dagger", in the Trades Ward, in WaterDeep.
Thelmaren (Wizard#2) is somewhere in Cormyr (where exactly is of no importance).
1-Thelmaren casts Discern Location to find Salamar. Without a problem, Thelmaren finds that Salamar is on the Material Plane, on Toril, in Faerun, in The North, in Waterdeep, in the Trades Ward, in the Inn of the Dripping Dagger, in room number-5. Case Closed
2-Salamar is in room number-5 etc etc... and he casts Rope Trick. Once again Thelmaren casts Discern Location. Now all Thelmaren knows is that Salamar is in an extradimensional space that is outside the multiverse of extradimensional spaces (“planes”).
Rope Trick Wins. Case Closed