LE absolutely does not have an obligation to keep the family updated on their investigation. Anything they tell them is usually for the purpose of keeping them calm and cooperative. If the family demands to know where the investigation is at any point, they may give them a few details, usually very minor, just to placate them, but for the most part, it's better for them not to know so that they won't have the problem of telling the media that they can't discuss the details publicly just yet.
Has the family been asked if Holly's phone was found, and they lied? Or have they just said they didn't know, or that they couldn't discuss it?
And why is it important to us to know if they found it? Whoever she talked to or texted with in the hours leading up to the abduction may not have any bearing on her disappearance whatsoever. In fact, there would be a pretty slim chance that she communicated with her abductor by phone just prior to her disappearance at all. Or the phone could have been destroyed making it impossible to get anything from it. Whichever, I can't see that information as benefiting anyone at this point.