You march into the gravel pits, sure you can't show off Mimikyu in a "Cave", but you can just train with Mimikyu on the sly, if Faba was using Mimikyu to make shadow pokemon you are sure there are plenty of tricks the little rag has.
You mark past hills, past people, until you find a nook, a pile of full rock pillars that have organized themselves into a small shelter.
You peek your head in, sand dribbling from the top of the shelter and you see.. a small red shovel.
You immediately scoot away from the sand dropping down, ball at the ready as the sand pile starts to form a mound.
A mound with a hole in the center, and to yellow eyes.
"Gha!!!!" Sandygast waves its small nubby hands at you, the shovel atop it's head like a toothpick through a olive (Albeit a living one?)
https://www.youtube.com/watch?v=u6_gm_mfelIYou are in combat!
The sand seems to shift aroung the Sandygast and you see sharp spikes in the sand. Perhaps a boobytrap? Or a weapon the Sandygast uses?
>Send out Mimikyu!>Send out Gremlin>Send out... yourself! You cursed Mimikyu you can speak ghost>Send out... your tail end! Run away! Your surronded by sand! 