I have had this problem and solved it this way. Push the loose T nut out of the fire wall then get a new T nut and a piece of hard wood approximately one inch square. Drill the hard wood and fit the T nut in it's center. Now thread a piece of string through the fire wall from the front until you have about 18 inches of string. Now thread the string through the T nut that is attached to the hard wood and tie something big on the string. I have used a nut too big to go through the T nut. You now have a piece of string threaded through the fire wall and then through the new T nut and a string tail of about 12 inches. The last part is obvious. When you pull the string from the front you will pull the square piece of hard wood and T nut up against the back of the fire wall so go ahead Smear some adhesive on the hardwood where it will contact the fire wall. After the glue dries you can pull the string out the back with the tail you left on.