Sorry to hear about this, matey.
Being a victim (got the tee shirt) of theft or burglary (which this is most definitely NOT, S.9(1)(a) Theft Act 1968 already having been quoted) is not pleasant and can be quite stressful as well as bloody inconvenient.
The aviation community is relatively small but like any cross section of society it has its share of complete tossers, either directly involved or walting around on the periphery; however, word does tend to get around quickly and if you publish your unfortunate mishap on as many forums as possible the chances are that eventually the toerag responsible or someone who knows the tawt will read about it.
I would also publish it on some boating forums and even look in the boating classifieds - as a rule liferafts tend to be of more use to the fish-heads.
I don't suppose you have a photo?