C.K Impact Driver T4928

This is generally my last resort with screws that refuse to budge with either a handheld or electric screwdriver bit. I only use it seldom, but when I need it I need it badly! Today I needed it badly with about 10 screws to remove, which had been in place for many years and had rusted into the wood. After the first screw had shifted I resorted to my handheld screwdriver to finish removing the screw, but in removing the impact driver, the bit flew off and landed I don't know where - I have hunted and hunted but can't find it, and I'm only too delighted to find that I can buy a replacement here. However, do you take care since although magnetically retained, the magnet is not very powerful at retaining the bit.