the trap door

So awhile ago when I was leaving school and before walking out the door, I watched Mr. Zulz take the cover of the heater by the art room. But the heater wasn't there, instead was a small wooden door with a master lock, clamped on the side of it. I stood there and watched Zulz unlock the tiny door and then he climbed inside and was gone. Then ponytail Dave waked up the stairs, put the cover (for the heater) back on and said you saw nothing kid and walked way. Puzzled by this, the next day when no one was around I went over to the heater took the cover off and the small door wasn't there just an old metal heater. I thought to myself this can not be right because just yesterday there was a door behind this cover. So I put the cover back on and went on my way. About three days later I witnessed Dave taking apart the cover and ripping out the heater. Then proceeding to board over the wall. This was to weird to see so I left. And that is that.