727 one bad clutch plate. Input to output washer half gone

I said my first thought was not supported.
You know it is possible to set that loaded hi-drum over the input, and miss to index the third clutch disc on the splines of the hub. You and I know that is possible.. But you and I know how this doesn't feel right, and so we keep working it until it drops the final plate.
But it has has happened that I have taken apart a trans in that situation, and it was working fine on the remaining two discs, the last one just warped concave . But the remaining discs were just driving on the outside edges. This works fine at Part Throttle, until the discs slip with a lil too much power applied.
From the first post with NO pics, and me not there to see, I originally thought this is what might have happened. So I said;
As to the clutch; Probably not indexed to the hub-splines properly right from the get-go. Pictures would be very helpful.
After the pics came up, I saw this was not the case so I said;
My first thought, not properly indexed, is not evidenced in these pics.
notice the commas.
I'm sorry if I confused anybody.