Its gone! was indeed the flexplate!

new one installed, old one in hand even now though i do not see any loose rivets! cannot grip and turn any them with a vice grip! only things i see that rattle around are the two (i guess they are dowels) threaded inserts, they are very sloppy, I wasn't there when they swapped it out, but threads are clean so i assume something was screwed into them!

I now however have a new issue, Wouldnt really call it an issue, but it bothers me nonetheless, car seems lethargic now! doesnt seem to have the grunt it used to! in my head maybe???? i can think of nothing trans shop would have touched that would cause this!
Brakes are all free, car creeps forward in drive, no pulling to one side. any ideas???

Engine is running fine, no missing, smooth idle