The Simlah Chadasha (Siman 18 Seif 16) writes that if a knife with a Chazaka was held unused for three days - and one then slaughtered with it (without checking if it is smooth) and then lost it, that knife no longer retains it's Chazaka, as we are afraid that it may have gotten rusty, and the meat is forbidden.
Does this still apply to modern-day "Stainless Steel" knives?