Could of been a very expensive washer

I am so pissed off right now I had to complain to someone that understands the magnatude of this. First off I have had problems with a roommate which I have since kicked out for being a non paying deadbeat lebanese gangbanger. He was pissed off but he has been gone for a few months now. So I am was finally ready to get my engine prepped for the dyno (I posted a few pics earlier of my 408w build) and as I used a breaker bar to set my crank triger it stopped. I turned it the other way and it stopped almost a full rotation around. I tried using a bore scope to see through the sparkplug hole but it was difficult. So I pull of my oil pan to look for clearance issues....nothing. I tore of my intake and heads to find a folded washer that was put in my spark plug hole.

Who would do something like that....