Im making a chat NPC im having a problem, FindFirstChild() only checks once. Help?

Script:

script.Parent.ClickDetector.MouseClick:Connect(function(player) -- Detect player clicked head.

    if player.PlayerGui.Chats:FindFirstChildOfClass("ScreenGui") == nil then --Here's the problem.

        print("giving") -- print when the Gui is succesfully given.
        local GUI = game.Lighting.SpyChatThing:Clone() -- Clone the Gui
        GUI.Parent = player.PlayerGui.Chats Put Gui in player's Gui
        GUI.StartTalking:FireClient(player) -- Ignore this

    else

        print("Already has the Gui") -- print if the Gui is already in the player's Gui

    end

end)

So, the script checks if the Player is already chatting with the NPC, by seeing if there is a "NPCChatGui". So, at first, it works, but the second time you clik the NPC 's Head, the script thinks the Gui is still active, but it's not.

Here's the script that closes the Gui

local Button = script.Parent:FindFirstChild("Answer")

Button.Activated:Connect(function()

    script.Parent:Destroy()

end)