Are there any hints about Locke's exact location in the World of Ruins?

I'm watching a first-time playthrough of Final Fantasy VI. The streamer is searching for Locke. He's found Rachel and the old man, but the old man only says, "Find the treasure, find Locke" (or something to that effect).

I know where Locke is, but are there any hints that direct the player to his exact location? Or is it to be found by chance?

(Locke is found at Phoenix Cave.)

Extra credit: What would be a good hint to give a player who's getting frustrated, without easily giving it away? (The player has found all other characters, so there's probably no other spoilers to be concerned about.)

Solution 1:

You first need to head to Owzer's Mansion to have a hint about where to find the treasure:

In the World of Ruin, if the player inspects Emperor Gestahl's portrait twice, they receive the key item Emperor's Letter, ...

which hints to the location of the Phoenix Cave.

This letter tells that the treasure is located in the Star shaped mountains, which is exactly the shape of the Phoenix Cave (location 17)