One thing I have learned from my mother (although it was more important for her when she was doing it for a living) is that I have a small wastepaper basket per project and I never throw anything away to do with it, even scrap threads, until I’ve finished that particular piece. I have this way managed to salvage a pattern piece that I had missed when cutting out (because I don’t do tracing!), and even used bits of thread for handsewing when I’ve run out. Although if I do lose a pattern piece, especially a small piece, the first place I usually look is Toby the Thug’s bottom!
I still can’t find my covered buttons though - but I’m not giving up!!!