I would think that if Yaddle is still alive, Luke would be the best source for a lead on where to find her.
And, while I shouldn’t speculate too heavily on Luke Skywalker’s discovery skills, we do know he gained possession of Jedi texts and quite a few other interesting things related to the Force in this time period.
Of course, I’m of the opinion that Luke shouldn’t be passing off Grogu to Yaddle, even if she may be the better candidate to train him, but if that’s what it would take to bring him into this series then so be it.