string expected, got nil??

local DataStoreService = game:GetService("DataStoreService")
local shirtData = DataStoreService:GetDataStore("shirtData")

game.Players.PlayerAdded:Connect(function(player)
    local clothesID = Instance.new("Folder")
    clothesID.Name = "clothesID"
    clothesID.Parent = player

    local shirtID = Instance.new("StringValue")
    shirtID.Name = "shirtID"
    shirtID.Parent = clothesID

    -- Load Data

    local data
    local success, errormessage = pcall(function()
        data = shirtData:GetAsync(player.UserId)
    end)

    if success then
        print ("Successfully loaded shirt data")
        shirtID.Value = data
    else
        print("Couldn't load shirt data")
        warn (errormessage)
    end

end)

game.Players.PlayerRemoving:Connect(function(player)

    local success, errormessage = pcall(function()
        shirtData:SetAsync(player.UserId, player.clothesID.shirtID.Value)
    end)

    if success then
        print ("Player shirt data sucessfully saved!")
    else
        print ("Couldn't save shirt data")
        warn(errormessage)
    end


end)

So in-game the player's shirt template is saved as the value of the string "shirtID". Error I keep getting is invalid argument #3 (string expected, got nil)