PLP, I'm fairly certain that the fish-acclimation process that the supplier did was against conventional and widely accepted practice.
I would call the supplier and let them know what happened at delivery time. I would do this at least to let them know as they may have no idea what the truck driver/delivery guy did.
In my experience with YP, I've known them to float when dead or distressed. I'm not saying that is a rule of thumb.
Another comment is that I had my pond for about 3-4 years, with heavy fishing, before I even knew I had YP.
You might be OK.
