Bizarre issue

[Phildoo]

After installing the new top end on my nightmare I ran it for prob about 45 seconds. Fired right up and responded to throttle very nicely, so I shut it down. Went to do a visual and see a fuel leak from the back plate on the front carb. I said screw it I will fix it tomorrow. So I pull the plugs to run another test and find pieces of an o-ring embedded in the spark plug for that cylinder.
I didn't pull the head off to check if it was the piston o ring but am now wondering if it somehow sucked the ring from that carb???
Is this possible?

 

[Dr Honda]

I don't know how... it's not like you could have sucked an O-ring past the tiny little holes in the jets, and there aren't any O-rings exposed to the throat of the carb.