A contact at Cornell Athletics was also checking with their "risk managers" about the possibility that Cornell could cover the damage, but she got back to me this afternoon with a no, as well. A shame, but this isn't something I could really expect. The tickets do, after all, state that I'm attending the event at my own risk.
The glimmer of good news is that a guy I spoke to in Nikon's service department says that repair to the D90 never costs more than $270. If I send my camera to them at my expense, they do a free repair estimate by visual inspection and trying the camera, and let me decide whether to proceed or not. If not, they send the camera back to me, no obligation. If they open it and discover more or worse damage, they'll send a revised estimate before continuing. If it's really true that a repair is never more than $270, I like the idea of a repair better than buying a new camera. (There's nothing suitable on Craigslist at the moment, or I'd consider used.)
If I do go for a new one, an exact replacement is about $750, and a newer, better model, which I'd seriously consider if I were looking for a new camera now anyway, is about $1,150. I don't really particularly feel like spending either amount right now, and among other side effects, it would put off the possibility of my buying a new laptop for a while, but it wouldn't kill me.