To be fair, most conferences are fungible. You can meet the people you'll meet there elsewhere, at another conference or at other events like meetups. If for some reason SIGGRAPH is really the one place where you expect to meet the folks you must meet, then yeah ditch the hike and go. But if there's other conferences you can go to and achieve the same effect, I would go to the other conferences, and go hike with my gf.