Hi ,Hunterdog , I’m happy to see you got the new engine
in, good video!! Logically there is no other explanation for that bolt , not stripped,bent or basically harmed in any way to be laying in the oilpan.
If both came loose there would have been damage from pounding for as long as it took to shed that bearing cap. The fracture of the failed bolt is clean and I suspect it was very sudden, not prolonged.
I can’t prove it but I also can’t think of any other way to explain the good bolt in the oilpan.