Is information which is semi-hidden confidential?
Where someone discloses information to the world at large, the circumstances of the disclosure remain significant. Even where information may have been disclosed at source, if public access to that information is in fact limited, a recipient of the information "should not get a start over others by using the information which he received in confidence. At any rate, he should not get a start without paying for it" (Seager Limited v Copydex Limited  RPC 349, at 368).
-E.g. Technical drawings are confidential even though they could be re-created by dismantling a sample (Terrapin v Builders Supply) and unencrypted information remained confidential, even though it could be lawfully reconstituted by someone decrypting the encrypted version of the information (Mars v Tecknowledge)
If, on the other hand, the information publicly available suffices so that no additional work is needed by other interested parties, then the recipient of the confidential information gets no springboard and so will not be restrained from using it.