is on the other side of the circuit board that you can see when you open the key to change the battery. The circuit board lifts out easily as it is not fixed in place. The
is about 16mm long by 5mm wide (gold colour winding). It should be glued to the board but if it has come off the windings could be damaged as they are very thin. If so it would need rewinding by hand. As I said earlier the number of turns is critical so difficult to do without the right electronic test gear. Have a look inside and if it does look damaged I'd be happy to take a look for you for the price of the return postage.