Zip, You are a pretty sharp ole cookie ! I think you are onto something. In my opinion i think the first owner does know something he is not telling.
#1 If the engine was 25 passes old it was put back together with alot of old parts. I would like to know how many runs were on it at the time it was freshened.
#2 It would be nice to know the extent of the freshen up. We already know that the pistons did not come off of the rods because someone would have picked up the loose wrist pins problem.
#3 It sounds like maybe the lifters were reused and after 25 passes it exploded a lifter or two. Not sure about the screw going through the engine. You would be surprised the damage roller needle bearings can do to an engine definately if you do not get them all out before you replace the lifter.
I could go on and on but i think you get my drift. This is just my opinion and i am not accusing anybody of anything. Thanks, Don