8 3/4 rear end confusion

I purchased a flexible magnet and was able to fish it to the bottom of the dif. Couldn’t get ahold of the button but each time I brought the magnet out, there was lots of ground up (flaky) material that got caught by the magnet. Now I’m thinking the previous owner had ran the car with the button at the bottom of the dif and completely tore it apart. I’ll be taking out the dif and cleaning it and may need to rebuild it. The previous owner had the wrong rear brakes on the car and had taken off the self adjuster but it still has stock bearings so I wouldn’t put anything past this guy. We’ll see… thanks everyone