2002 Isuzu Axiom the oil cooler line to the radiator blew without warning

Hello all, I have a 2002 Isuzu Axiom 2w drive. I've owned it since new and have babied it with good maintenance, oil changes etc. I had the transmission serviced at 45k miles and had just about reach 90k miles for my next service of the tranny. Unfortunately the week before I was going to take it to the dealer for service, the oil cooler line to the radiator blew without warning. No leaks or other signs were evident before the failure. Since it was the pressure hose from the tranny that split open, all of the fluid was dumped immediately had the car coasted to a stop. We had it towed to the dealership here in West Palm Beach and they replaced both hoses, the filter, gasket and flushed the tranny all of which came to $507. With the towing charge, I'm out about $600. My question to the group is this: Should I have expected this line to let go this soon? How many others have blown with less than 90k miles? I'm still covered under the 120k mile / 10-year power-train warranty by Isuzu but the dealership said that this pressure line is not part of that warranty. Should I appeal to Isuzu for my out of pocket expenses?