Yes, the pistol is plenty good. Your potential problem is skill in a high-stress situation.
If the lion's taking of the dog was more than a couple of days ago, odds are that he's moved on or is not hanging around in the near vicinity. A deer or elk? Yeah, a lion will hang around for up to a week to keep guard over his supper, but a dog wouldn't last long.
Lotsa luck in finding tracks, unless there's snow on the ground...
You're from BATFE? Come right in! I use all your fine products!