Given there was so many people there it's almost impossible there wasn't a lot of infected people there. I guess the question is whether you sat in very close proximity to people.
Also how long ago was your 2nd vaccine. Of 2-3 weeks plus then all should be well and illness relatively short.
Yes, I'm sure there were many people infected, no doubt. Walked around the whole track, masks on when in busy queues/toilets etc, sat in camping chairs, sat in a few grandstands, the busiest being fp1 at club. Was on the end of a row with no one immediately next to/in front of us, but obviously it was busy. There was a fair breeze through the stands all day so I guess the delta variant is just so transmissible that even outside in a breeze doesn't stop it.
2nd vaccines mid June. Took the risk given most of it was outdoors, Silverstone tends to have a breeze etc. Don't expect her (or me) to get much beyond flu-like symptoms so happy the vaccines are doing well in that regard.