Attach ball sprite to NPC head

I’ve done this (taken from sent_ball):

cl_init.lua
[lua]
include(‘shared.lua’)

ENT.RenderGroup = RENDERGROUP_TRANSLUCENT

local matBall = Material( “sprites/sent_ball” )

/---------------------------------------------------------
Name: DrawPre
---------------------------------------------------------
/
function ENT:Draw()

    self:DrawModel()
local BoneIndx = self:LookupBone("ValveBiped.Bip01_Head1")
local BonePos, BoneAng = self:GetBonePosition( BoneIndx )
	
render.SetMaterial( matBall )

local lcolor = render.GetLightColor( BonePos ) * 2

lcolor.x = 255 * mathx.Clamp( lcolor.x, 0, 1 )
lcolor.y = 255 * mathx.Clamp( lcolor.y, 0, 1 )
lcolor.z = 255 * mathx.Clamp( lcolor.z, 0, 1 )

	
render.DrawSprite( pos, 32, 32, Color( lcolor.x, lcolor.y, lcolor.z, 255 ) )

end
[/lua]

But it draws only the model without ball. Why?