Wow a frustrating problem. I knocked a freeze plug in the coolant jacket in the rear of the engine a 350 GMC. I have a very powerful magnet that is a 1/4” wide and a 1” long. I attached it to the end of some needle nose pliers. The magnet grabbed the side of the block and came off the needle nose. Now I have a magnet and the plug inside the engine. To make a long story short I got an “S” hook and got both out. Then I dropped the S hook inside. No idea where inside the engine. Help!