You could get a cheap bore scope and go through the oil drain back holes in the head. Peek at each lifter and lobe. The filter might have caught a bunch. Cut it open.
Already did that actually, just didn't add it to the post because it was already a novel.
It was quite difficult to get right down there, but from what I could tell, it looked alright. I may try again though and also check cylinder 3 now as well. Good idea on cutting the filter.