You will either lose it in the pit, or you it will be knocked off by someone in the crowd. (By accident of course. Just because someone is going to see a bunch of rock bands, doesn't mean they are jerks.
And if you are going to wear jeans, wear RIPPED (at least ripped) SKINNIES! If you wear regular jeans you are going to get hot. If your jeans are ripped, you won't be as hot, considering you are letting more air onto your legs.