So sorry that Tom didn't make it. Purplemuffin is right, there is often internal damage going on that we can't predict without doing an autopsy.
Bacterial infections can be difficult to diagnose and treat. I have lost a handful of fish to accidents that were my fault, but in this instance, you did everything you could even with the absymal advice of LFS employees.
Most fish owners wouldn't have bothered seeking advice or attempting treatment. Tom was very fortunate he had someone willing to go that extra mile for him. So sorry for your loss Shemumbles.