I had one pop out of a customer's car many years ago. I don't know the history of it, as in who installed it, how long ago, and how tight they made it. Since there's a brass strap that gets pushed into the block and becomes the nut to tighten it down, there's going to be a lot of stress on it. I wouldn't trust them for anything more than an emergency or temporary fix until you can put the right core plug back in.
Also be sure to replace the antifreeze every two years. Antifreeze will always be antifreeze, but it's the additives that wear out in about two years, namely water pump lubricant and corrosion inhibitors, and acids normally form that will lead to corroding that brass strap on the rubber core plug.
Monday, February 2nd, 2015 AT 1:10 PM