for me i basically thought he got useless as soon as I reached terrajuma. i stopped using him but then someone in the forums told me he will evolve there . and now im using him again for the rest of my game. also if you get heartscales you can get an amazing moveset for vikavolt.
they changed it for this ep.
you gotta find her a few times, then their will be a cuttable tree to the left of the kecleon (u have to walk a bit), you will have to interact with that tree a few times. and then she will appear in front of the cave.
get magma drift --> proceed story --> if that doesnt work its prolly bugged --> change to old version --> go to magma drift mountain -> get the item from the duder -> switch back and continue in that cave.