Leprechauns. You know it because springs that can't be found even with the honking big speaker magnet will suddenly appear plain as day a week or so after you got a replacement spring installed.
Actually I think I've had better luck with the big Mag Lite held at a low angle but still...
1911 mainsprings, Browning Hi power mainsprings. A fella' needs extra.
BH Springs Inc. has a good tool for the BHP.
Then you get to the really small ones. Added to that aging eyes. Big fingers.
The light trick across the floor. I forgot to mention that. It works. sometimes.