When he said he had been unable to find the light (which necessitates that there was a search), and equated that to Sora looking for his personal light before Sora had done more than say he was searching for something (without even specifying whether it was a person, a thing, a feeling, The Light or his own light).
That technically indicates there was a search, not that there is one. Rendered past tense and all.
That his search for light was rendered in past tense while his search for someone is present is part of what indicated to me the two were unrelated.
EDIT: And it's even more unrelated what with losing sight of the light instead of not finding it.
And Ryu, I find it counter-intuitive to conclude that Cloud was speaking of The Light as a general concept when the terminology of the game includes that concept as well as the concept of personal lights. It just doesn't jibe with a proper literary analysis -- which is going to assume the exact wording "your light" was chosen instead of "the light" for a specific reason, and as a superior choice for whatever the storytellers wanted to convey.
Does this approach give the storytellers too much credit? Perhaps. But I think we will all agree that when it comes to characterization, Nojima is pretty damn good at getting across what he wants the audience to take away. Whatever people might think of his plot devices and choices in events for progressing a narrative -- and there's plenty of disagreement about those (e.g. the orphanage plot twist in FFVIII) -- his dialogue is typically effective.
Cloud uses 'Your' to refer to Sora's light, yes, but Sora uses 'it' to refer to the Light Cloud speaks of twice. Cloud also used 'it' and 'the' when referring to the light relevant to him. This sounds incredibly odd if Cloud intends to be speaking of a person, much less Aerith. Them would make far more sense if you wanted to keep it vague, instead of rendering the light an impersonal object.
But my point isn't to suggest that the light must be 'The' light, but rather that Cloud never actually expresses that he has been searching for light, just a lament that he lost sight of it in his use of darkness to find X. Sora cheering him up saying 'You'll find it' doesn't require that Cloud be searching for his light. To me, it actually makes more sense as words of encouragement in response to a defeatist tone. 'I lost sight of it' 'You'll find it, get searching' and all that.
The overall point isn't that the elements are not there, but that you have to look at those elements funny, ignore other elements, and make assumptions that nonexistent elements are true for this one to arrive. Especially after KH:FM dropped and made it explicit, much less KH2.
Speaking of Noj's dialog, we typically use the English version. Does the JP version also say 'your?' I don't wish to split hairs, but if we are concerning ourselves with the context of a single word, it might be worth comparing versions.