HMMMM that aint good mate! you sure you aint been torquing in nm instead of lb/ft
were they standard bolots you used or A.R.P ones? it is VERY strange that the main cap/bearing has come off!
As least it wasnt a big end and everything seems to be ok..
Deffo get everything checked though as there is NO WAY that should happen.. even if youve use the same main bolts 10 times!