transmission not shifting correctly

I love my car and this is the first problem I have had in three years of owning it. That said, this was a very scary experience that made me feel like the car was in control of me. While accelerating onto the highway, I used the paddle shifters to upshift while I depressed the accelerator. The engine began to rev higher and accelerate even with my foot off of the pedal. The RPMs were stuck at around 5000rpm. The car would not slow down as expected with the brake pressed. I managed to get around the traffic ahead of me and I exited the highway at the next exit (about 1/4 mile total) and was able to slow the car down and turn the car off. When I turned the car back on, the engine was revving very high and the brake pedal was stuck down. After calling for roadside assistance, the car restarted with no problem present.

Upon reading the receipt from the first dealer I went to, it was clear that they didn't understand what had happened. They drove the car and couldn't reproduce the same. I'm having the car reassessed by another dealer who at least has found that the transmission fluid is burnt...no surprise there. And it supports that the first dealer didn't bother to look.