personally i dont believe that you have lost your ability...i believe that you went through a 'dry spell' and when the dry spell ended you let yourself believe that you couldn't lucid dream anymore so u eseentially gave up for a while and lost the ability...there are many cases which r just the same...

so the point that im trying to get at is that u havent lost the ability you just have forgotten it, just like learning another language...if you dont use it for a while you lose your familierarity with it......so in other words, all u need is to jog your memory of lucid dreaming and u should be able to do it well again.....