Yeah, it definitely sounds like the previous owner ran the snot out the bike and maybe even dumped it a few times if, as you say, it seems like it was run on its side.
In any case, I don't think the sounds you heard and then started to feel are reflecting what most are experiencing on this thread.
It seems like you had a very clear progression of sound to vibration (metal on metal) to failure.
That sucks - hope you were able to square it away properly!
'12 R1200GS Adventure
'06 Ducati 999S
'11 Harley Street Glide - gone and mostly forgotten
'07 Tuono Factory - gone but not forgotten