82-year-old Vickers -- who famously starred in "Attack of the 50 Foot Woman" -- was reportedly a recluse ... and neighbors say they hadn't seen her since last Summer.
A neighbor decided to inspect the house after noticing old letters and cob webs in Vickers' mailbox ... and noticed the model's badly decomposed remains in an upstairs room. The neighbor claims a small space heater was still running when she discovered the body.
Police say they are still investigating the cause of death -- but they do not suspect foul play.