Tire Bubble problems of the 2005 Mercury Grand Marquis

I have toyo versado lx tires on my 2005 Mercury Grand Marquis p225/60/r16 98t dot dot 73a6fwv4410. The tire has developed a bubble in the tread on the inside of the tire. I pulled the tire out of service before any failure or accident. Toyo tires is not even interested in hearing about any part of the problem. They just tell me it is out of warranty. I was not making a warranty claim, but am disappointing that they want nothing to do with any of the details of the problem to see if this is an isolated incidence or whether there is a problem with these tires. I am quite sure that there are alot of these tires that are approaching 5 years old that are on the road. I live in kingman arizona, and the car is kept in a garage out of the sun when parked. It is not parked out in the sun regularly during the day either. There has been no accidents or flats on this tire and it has approximately 35,000 miles on it. The remaining tread depth is aprox 5/32 of an inch.