Try pulling out the interior latch handle and looking for the end of the cable with needle nosed pliers. You will have to move, and possibly destroy, the rubber seal, but if the break is at that end you may be able to catch it.
If that doesn't work, then try calling the police or someone else experienced with a slim jim.
Final solution would be to remove the seat from the opposite side...not easy! Then you should be able to remove the door trim panel to access the latch.
This seems to happen a lot with the L322. Is it wise to just go ahead and replace all the hardware as a preventative measure? I am just waiting for a delivery before replacing all my exterior cables, but have realised the rear one that is inoperative is actually still connected, I can 'feel' it. Now that the car is not very valuable, I am thinking I may as well add an easy in option, like a hole somewhere or a 'secret' cable.