The nut on the outside was a bit loose, then when I took the cable out and put the guitar away, the jack fell inside the body. Not sure how I can get it out and reattach it to the hole without completely taking apart the guitar.
The guitar is an Ibanez AK95 so has f-holes on each side, which don't really seem big enough to allow me to root around inside the guitar.
Even if I did have to take the guitar apart to fix it, how would I go about doing this? I can't find anything on the net discussing how to take apart semi-acoustics or even acoustics, only eletric guitars.