I'm basically implementing a script where it plays an audio object and shuts down the server after a minute if the main object in the game goes missing.
while true do
if workspace["Core"] then
print("Core Exists")
else
print("ERROR: CORE MISSING")
script.Parent:Play()
local H = Instance.new("Hint",game.Workspace)
H.Text = "ERROR: Core Model is Missing or Destroyed. The server will be shut down in about 1 minute."
wait(60)
for i,v in pairs(game.Players:GetPlayers()) do
v:Kick("Server was shut down due to the Core being missing or destroyed.")
end
break
end
wait(1)
end

2 comments
Note: I've also tried "Instance:FindFirstChild", "workspace.Core", and "if workspace.Core == nil then"
if workspace:WaitForChild("Core", 3) then