How Could I Be So Stupid/Careless?

Talk about getting distracted. A friend called me up a couple of days ago. He installed a new 440/727 engine and trans into into his car, and tried to fire the engine. The engine would not turn over although the starter would spin. Three different starters same thing. I went up to take a look. During the build/install he had gotten interrupted and forgot to install the converter to flexplate bolts. Starter would engage the ring gear, converter would spin, but not the engine.
I had a similar issue one time. Had the converter bolts installed finger tight, and got interrupted before putting Loctite on them and torquing them. After the second pass at the track, thought I had a rod knock.