general problems of the 1998 GMC Sonoma

I lost the tread on one of my toyo tires as I was driving down the freeway. It completely separated from the tire! it was the passenger front tire. Thankfully, I was able to steer to the emergency lane and call for help. I've already had it replaced but the dealer I went to (discount tires) where I purchased the defective one told me they are good tires and convinced me to buy another toyo. Now I'm worried.