Gives nil value or says that player is not valid workspace, why?

{{'storebuild','sb'},{'stores build of player in storage.','DiGamesChannel'},2,{'player'},function(pl,args)
    for _, player in pairs(args[1]) do
        local Tool = game.Workspace.player["Building Tools"]
        local Core = Tool.Core
        if game.Workspace:FindFirstChild("BlobbyblobBuild_"..tostring(player)) then
        Core.Selection:clear()
            repeat
        game.Workspace:FindFirstChild("BlobbyblobBuild_"..tostring(player)).Parent = game.ReplicatedStorage.Cleared 
until
        not game.Workspace:FindFirstChild("BlobbyblobBuild_"..tostring(player))
end
end
end}

it must clear building and selection, but it cant find player. what i did wrong?