it is a good question jacques, don't believe any one because whatever they say, they don't know!
this is one the major problems with quantum mechanics, it has a more famous form as "the cat of shredinger". it goes like this - if you close a cat in box it will eventually die. the question is when. the problem is that to know that, we have to open the box. saddly, acording to quantum mechanics this is the moment the "wave function" of the cat collapses and therefore it is the only moment we can conclude whether the cat is alive of dead. it is logical, but we also know as a fact that the cat will die eventually and this will have nothing to do with us opening the box. so the answer is - we don't know when the cat will die - and in relation to your question - we don't know where the photon is, or what it's "wave radius". we could only assume. and acording to quantum mechanics, it could be anywhere in the universe.