After hearing some players have issues with less than the intended 20, I decided to wait until the past weekend to claim them, which I counted each one to ensure that I received them all. You may be checking your "Recently Acquired" tab to count them, which will not be accurate as I believe either some finishers or emotes do not show up there, which only says 15 for my tab even though I know I received all 20. Definitely that trail effect cosmetic isn't showing up there, and it's still sitting unwrapped in my inventory.