Legendary Snowball Event

So I wake up this morning and log on to League. I was really excited to see one of my friends had just gifted me a mystery skin. Better yet, it was a legendary skin! I remember reading about how if you get a legendary skin, you're supposed to get an extra mystery gift. But I was disappointed to find that I did not obtain any additional skins. Not that I am complaining about receiving a legendary to begin with, I am simply curious why I didn't receive the extra one. Further clarification would be appreciated.