temporarily lost drive gear (auto transmission) on 1995 Buick Riviera

While driving on the interstate at 70 mph I suddenly lost drive gear 100 miles from home. I limped home in 3rd gear going 52 mph at 3000 rpm. After the car sat for a couple of hours I drove it at 70-75 mph and it went into drive and overdrive just as it's supposed to do. I don't want to go on a long trip for fear it will happen again. These problems are never self correcting. Any suggestions?

Asked by for the 1995 Buick Riviera
ive been riding in 3rd gear in my 95 buick riviera for years. i read n consumer guide auto that this type of transmission on this car has a tendency to shift into neutral at highway speeds due to a problem with the internal shift valves
http://consumerguideauto.howstuffworks.com/1995-to-1999-buick-riviera-2.htm