[Solved] Problem with script not recognizing players backpack?

I've made a detector script which sees if a player has a tool in their backpack called "LavaKey" and then if so opens a door by making it invisible and then waits 8 seconds and closes it. The issue is I cant seem to get the line that sees if the key is in the backpack correct and when I run the game and step on the detector I get an error on line 10 saying that "Backpack is not a valid member of Model" but then after that I get no more errors. (That error may be referring to the door thats on the detector or something but it doesnt have a humanoid. Anyone know what I need to fix? Thx.

local detector = script.Parent
local door = game.Workspace.LavaDoor
DB = true

detector.Touched:Connect(function(hit)
	if DB == true then
		DB = false
		if hit.Parent:FindFirstChild('Humanoid') then
			local hum = hit.Parent:FindFirstChild('Humanoid')
			if hit.Parent.Backpack:FindFirstChild("LavaKey") then--here
				door.Transparency = 1
				door.CanCollide = false
				wait(8)
				door.Transparency = 0
				door.CanCollide = true
			elseif not hit.Parent.Backpack:FindFirstChild("LavaKey") then
				hum:TakeDamage(20)
			end
		wait(2)
		DB = true
		end
	end
	
end)