The respawn time for each moppet is ~30 seconds, so if you are doing this quest in a group and the moppet does not reappear after a short period of time, it is in one of the other locations. Also, if you are doing this quest as a group, only one person can click on the moppet at a time, and only that person will get the update.
If you kill the deputy moppet out of order it takes 15 minutes to re-spawn.
Just west of the river among the tainted maidens ( -341, 10, 58 ) Copy/waypoint -341, 10, 58
In Roundbelly's General Store in the little storeroom, guarded by 3 linked 37 ^ heroics. ( -200, -9, 105 ) Copy/waypoint -200, -9, 105
To the south of Roundbelly's General Store among the roots of the stump house (Between the tree and the root above southern end of river) ( -200, 0, 222 ) Copy/waypoint -200.30, 0.10, 222.13
Along the south wall amongst the corrupted halflings ( -68, 9, 165 ) Copy/waypoint -68, 8.5, 165
Next to a tree east of the waterfall on the northern border of the zone ( -235, 4, -213 ) Copy/waypoint -235, 4, -213
Hunt for the marshal moppet. He's a 35^^-39^^ heroic with a direwolf friend of the same level. He can be found running around the roads in Rivervale and frequently passes The Fools Gold ( -70, -17, 2 ) Copy/waypoint -70, -17, 2 and Digg's Tall n'Stout (aka The Loom) on a very rough 10 minute cycle. ( -192, -19, -12 ) Copy/waypoint -192, -19, -12
Starts his run at ( -404, 0, -116 ) Copy/waypoint -403.65, 0.02, -116.33
Also spotted at ( -427, -1, 143 ) Copy/waypoint -427, -1, 143 and ( -419, 0, 213 ) Copy/waypoint -419, 0, 213