At the end of my fuse

I have spent a totally frustrating day. I live on a narrowboat, which has a 12 volt DC electricity supply. Some time ago, a fuse went, losing me the lighting and cigarette sockets at the front of the boat (under the tug front). The description the previous owner and constructor of the boat left me says that there are four fuse locations on the boat - one multi fuse in the engine room; and one for each spur of wiring he had installed; one in the airing cupboard to supply the bedroom area; one under the sink to supply the lounge area; and one in the stereo alcove supplying the front lighting. I have located and checked all the fuses except the last - which is the one I am sure has gone. But can I find the last fuse! I have spent today removing equipment from the area of the stero alcove, investigating every dark corner and crevice I can find with a powerful torch, looking for the fuse. It is nowhere to be found. So tomorrow I will have to start shifting all the items I have stored in the tug front to continue my investigations - which of course are hampered by the fact that there is no light in any of these areas because the fuse has gone. Grrrrrh!!