Thought I would share my experience with this quest, perhaps it has been changed over the (many) years. Playing on a progression server now, and I'm hoping this information will be useful for others doing the same, especially considering the speculative, old, and bad information that seems to surround this quest.
Basically all of the prior information I read about this quest neglected the distinction between "a froglok escort" and "Froglok Escort".
"a froglok escort" seems to have nothing to do with this quest at all, it's the special one with caps that you're after. It seems Froglok Escort can spawn a few places in typical mob spawn locations. My two spawned right around +2575, +1402. After the Froglok Escort spawns, it stands completely still in place unless it needs to run from combat. Any hostile mob seems to aggro on the little guy when they wander by, skellies, large mosquitos, maneating plants, maybe some others. The interesting and important part is a little difficult to describe, but I'll give it a shot. It seems that somewhere out in the swamp there are a few spawns that are likely completely inactive until the Froglok Escort spawns. Once he spawns, you will some mobs come running from a specific direction towards his exact location. These spawns out in the swamp are what can spawn the escaped froglok slaves that you need. The issue is, the slaves have some placeholders. Skeletons, leeches, iksar marauder, and a small handful of other typical swamp creatures will all come rushing (full run speed) toward your Froglok Escort friend. What you need to do is protect the Froglok Escort, if he dies the whole "event" is over and you have to get another one to spawn. Kill everything that rushes towards him as quickly as you can, and eventually some of them will pop up as escaped slaves. I believe as long as Froglok Escort stays alive, these mobs will keep spawning and rushing after him.
TLDR: Kill stuff around +2575, +1402 until Froglok Escort (with caps) spawns, defend him from meanies and eventually escaped slaves will show up.
Reposted from the quest's page.