If you have an AC membership, the counter staff at SFO has been good about issuing a pseudo boarding pass to let you through security, if you're flying on a different carrier. Although, someone had mentioned that now the TSA at T2 will let you through by showing a same day boarding pass at SFO with your AC card. However, all of this should become moot within the next couple of months, as the airside connector between T2 and T1B will be opened.