How do I check if player left?

I've asked questions about the same script, but this is a different section. Previously a kind samaritan helped me find a random player and have the ability to change values in the player, but I cannot detect if the player left the game so I can wrap up the game.

-- This selects the player "p[selected_value]"
local plrs = game:GetService("Players")
local p = plrs:GetPlayers()
local selected_value = math.random(1,#p)
p[selected_value].Settings.Tagger.Value = true

I tried checking if the player is nill, but that had no outcome

local waiting = 30 -- amount of time to count down from
for y = 1,waiting + 1 do -- this makes it stop at 1
	wait(1)
	if p[selected_value].Settings.Tagger.Value == true then -- checks if he is tagger, if not he has died. 
		main.MainText("Time remaining: "..waiting) -- calls a module script to change GUI
		waiting = waiting-1 -- decreases amount of time left 
	elseif if p[selected_value] == nil then -- checks if the 'tagger' left
		main.MainText("The Player has left.")  -- calls a module script to change GUI
		wait(2)
		break -- breaks the loop, thus ending the game. 
end