BBM
That isn't obvious AT ALL! In fact, statements from and actions by FHPD strongly imply that they know they have their perp. I believe they have quite a bit of evidence, but it may well be that this prosecutor is afraid of the unrealistic expectations of jurors due to the so-called CSI effect.
Your suggestion that they may have "no" evidence connecting him to Danielle's disappearance is disingenuous. It's a given that they have evidence connecting him to her on the evening she disappeared, otherwise they would not have searched his house--would not have confiscated his mattress, his vehicles, and his floorboards.
And let's not forget, they announced that Danielle was the victim of a crime almost immediately after they searched the security guard's house.