I have 'lost' a length of CAT5 cable, one end is where it should be,
but the other it does not appear where it should in the comms
cupboard.
My assumption is that the company I had in to fit the fitted furniture
in the study have trapped this behind one of the built in units at
some point.

I don't want to rip out all the units - not an option. I could cut an
access hole in the back or base of one of them - where for example it
would be hidden when drawers are in place.


But it would help if I could get a good idea of where the cable is (or
where it's held up) ... I have tried using a tone-tester down the cable,
but that won't work as soon as tone lost as soon as cable disappears
into the wall.
Anybody any suggestions of something I can inject 'into' the cable,
and how I can trace it ?

( The cable is a foil screened CAT5e )

Otherwise I will have to run in a new cable ... and this would be so
damn annoying having built the rest in.