If you start Growf's line before journeying to Fens of Nathsar, Growf won't instantly offer this after the last quest. Once you return from Search and Rescue, Growf should then offer this quest. If you don't have a Gathering Goblin, you won't get this quest (update Mar 18, 2022 - this quest will be offered even if you do not have the gathering goblin ability).
Steps[]
Growf says gathering goblin may be unhappy and asks you to verify.