Hello my name is Vinny.
Im new here and have a question about a blown tranny. It has been bugging the crap out of me. Im really hoping some one here can put my mind at ease with this one.

To start I own a small mechanic shop in SE Wi. I dont normally touch transmissions aside from replacing them but this one is a special case.
My neighbor has a 2000 GPrix 3.8L with roughly 90k on the chassis. The Trans looks like it was allready replaced with one from a salvage yard. So its hard to say how many miles are on it. More recently he brought it to another shop for intake gaskets, because I was busy. Well long story short. Due to some bad advice from the guy. It wound up at my place with multiple rods in the oil pan 2 weeks later. Obviously It was seized so.. In order to remove the trans I had to flip it upside down and remove what was left of the connecting rods.

I swapped the motor and 2 days later the Trans started making a metallic screeching sound when it warmed up. His wife drove it short distances daily like this for a little over a week. By the time it got back to me it was horribly loud. At first I thought it was a pulley or something but quickly eliminated those as a cause. When underneath the car and the covers were removed from the torque converter it was loud enough to hurt your ears. The noise remained unchanged regardless of the gear or if it was moving or parked. I flushed the cooler lines again to make sure there was no blockage. The fluid looked pretty good as well. After I eliminated those. I thought possible causes could be the torque converter or bad solenoid/s. So I decided to pull the trans back out.
While removing the trans, I removed the CV axles and noticed the output shaft on the driver side of the trans had serious play in it. (I didnt notice any before)
After removing the trans I Pulled the pan and it had significant build up but no large chunks of metal. I continued to disassemble the trans. There is obvious bearing failure on the drive axle. The gears in the differential are a-little chewed up, and seem sloppy. Some of the clutches and components closest to the diff show signs of heat fatigue. But aside from that the rest just looks well worn. I didnt find any catastrophic failure like I expected. Not only that but none of those explain the screeching while parked.
The torque converter was full and seems to be in good order. I havent tested the solenoids. But at this point it looks like it will be cheaper and easier just to replace the trans with another used one.

Now heres whats eating at me...
Is there any possible way this is my fault?? Or just a horrible coincidence??

Obviously when something like this happens 2 days after you performed a major repair all fingers point to you. Whether its your fault or not.
But honestly, Im completely stumped on this one. And its driving me crazy.
Because aside from it being upside down for roughly a half hour, re-filling what fluid leaked out, and flushing the cooler lines. I didnt touch anything else on the trans..
Any thoughts?