Did not receive random legendary skin for day 10 of anniversary

its not a random skin

its an ANNIE skin, you dont open it, just check your collection it auto adds it

I had the same issue, but I figured it out! So, it will be mixed in with your skin shards. It will look exactly like a skin shard, but when you hover over it the text will say "skin permanent". I assume it did this because I received a legendary skin for a champion I didn't own so it put it with the skin shards. I have 58 skin shards and it was the very first one, yours probably will be the first one too. If not, just hover all the skin shards with a red dot under it (which indicates legendary) until you see the one that reads "legendary skin permanent".