How the fudge did Sivir get her crossblade back from Cassiopeia????!?

Ever seen someone leave their keys in the door lock? Same thing, with Sivir's blade being the key. In Cass's defense, she was pretty distracted after opening that door...

I dont think Cass took the time while being turned into a mersnake to hang onto the key, i mean, a magic venom changes the very fabric of your being, would you cling onto a key (already used for the only thing it opens) like it was the only key Link couldnt break? It was probably just in the dirt when she was brought back

She killed a cosplayer and took theirs.

I assume when Cass got turned into a snake fetish?