retrieve a washer dropped in the gearbox..cant believe i did it .

[37coop]

hi guys ,the title says it all , iswitched working on my 51 f1 to do a bit on my 39 coupe,i took the lid off the gearbox which is fully installed in the car to put the gear lever in ,I picked up one of the lid bolts and the washer slipped off the bolt into the hole,after 40 years of playing with cars and bikes I cant believe I would make such an error (I,m sure I,m not the first)I have fished around inside the box with a small powerfull magnet on a rod with no luck,i cant see it resting among the cogs ,I obviously cant leave it there ...any ideas ?....cheers ,jim.