I hope this letter finds you well. After some digging, I've discovered some information on those who wrote that note you recovered.
Samla's father leads the Forsaken and Trolls who make the pilgrimage to Thunder Bluff in the ways of his faith. His name is Miles Welsh, and you can find him with his fellow undead in the Pools of Vision.
Torgal, meanwhile, is survived by his cousin, Elissa Dumas. She is a reclusive sort from what I've come to understand; she spends her days in the Temple of the Moon in Darnassus.
I urge you to visit whomever you can, <name>. They may never have learned of Torgal or Samla's fate.