You absolutely won't get any sympathy from me as I am an Oregon fan
My daughter is a student at the University of Oregon and I am a big time Ducks fan. I'm still smarting from the championship game last year.
That being said, I attended the Track and Field Championships at Hayward Field at the University of Oregon (OK, it's not Autzen Stadium where they play football) a couple years ago. I rented a big guns lens (I think it was the 80-400 or something similar) but not THE BIGGEST LENS they had so I could get some decent shots. The folks at Pro Photo Supply here in Portland recommended that I choose the smaller lens so as not to raise suspicion. I carried it with me in a bag where I had carefully placed a few feminine hygiene articles, which was also recommended to me by Pro Photo Supply. I realize, of course, that you can't do this
At any rate, the bag was searched at the entrance to Hayward Field, I was allowed in with the lens, and was able to get a few shots of the track and field runners.
That was my experience. I did not bring a big lens to the one game I did attend last year at Autzen Stadium where the Ducks played at home and won.