Forum Thread

So I was setting up a couple of Megas for prep to move into my party for leveling and one of my Mega Stones went kaput. I attached one to my Flygon successfully, leaving me with two (I had three to start with) and when I went to attach one to my Mega-able Gallade it SAID it attached and took it from my bag, but didn't ACTUALLY attach it to the Gallade. A second attempt with my remaining Mega Stone did work though, so not quite sure what happened?

( If this is the wrong forum I apologize. )

I think it's because you mega evolved your Gallade with that 'poofed' Mega Stone
You mega evolve a mega-able Pokemon by raising it to level 50 while it is holding a Mega Stone. I guess you gave Gallade that Mega Stone when it was near level 50, so after you gave it the Mega Stone, the next interaction raised its level to 50, making Gallade Mega Evolve. That Mega evolution consumed the Mega Stone you gave to Gallade
When you attempt to give the already-Mega-evolved Gallade then of course it'll show that it's holding it
(And yea, you're in the right subforum ^^)

Lol. Wow, I didn't even realize he was already Mega-Evo'd. *face-palms* For some reason I was thinking he hadn't yet, which was why I posted this in the first place. Forgive my dumb! And thank you, Rice!