Miles, while trying to track down what happened to Patricia, got caught by Geo and his thugs fighting a slim Ninetales man. One of the electric-types following Geo let out a blast of Electric Type energy, hitting the Eevee square in the chest.

Actually, square in the pendant. The one with shards of deactivated evolution stones.

The Type Energy surged through the stones, then through Miles' body, causing him to evolve. Seeing him spark with energy alongside the Ninetales, Geo and company decide to fall back. The Ninetales looks with concern at Miles as he stumbles, and helps him home. Miles is too out of it to ask how the Ninetales knew where he lived.

Miles woke up in the morning a normal Eevee. ...with a few changes hinting at his adventures the night before helping keep it from being just a dream.

Art by  dragoneer