It doesn't matter if you brought a different book for each piece you are playing throughout the service. It's going to happen. The pastor is going to say something in his sermon that very directly ties into a song for which you didn't bring music. A song you know you have in that one book. You might drive back to your house between services to get it. You might write the entire service off as a missed opportunity. You might just pull out the hymnal and improvise on a wing and a prayer during the offertory. There is no cure for wanting that one book.... (Unless you live across the street and can send a gopher to get it for you.)
True confessions of a Lutheran traveling church pianist