Smolderweb Hatchling and Worg Pup are (temporarily) unavailable in-game. Due to the change to the zone, the quest chains and rewards were removed from Burning Steppes, leaving collectors with no way of obtaining these two companions post-Cataclysm.
However, we have some potentially good news from the PTR! With patch 4.0.6 a new item was discovered: Smolderweb Egg. Could this be a replacement for the item that previously taught the Smolderweb Hatchling? While it seems likely, there is still no confirmation if it will indeed replace the hatchling's carrier or how this newly discovered item will be obtained.
The Worg Pup has also yet to be rediscovered or found, but we remain hopeful that both companions will be making a return in the future.
Smolderweb Hatchling Update
January 21, 2011