Let me preface this by making a statement: I hate CPS and CPS hates me. In the county where I practice, all of the social workers know me by name and face, as do their attorneys; some of them fear me, some of them despise me, and some of them respect me, but none of them like me. I understand the necessity of their mission, but they are, in my opinion, a broken operation that is beyond home of repair, and they and the laws that they operate under need to be completely dismantled and replaced with something completely different.
So you know where I am coming from when I tell you the following: I do not see facts that would constitute child cruelty, child abuse, or child neglect
on behalf of CPS based on what you have said. The police have the legal authority to take a minor into protective custody if there is probable cause to believe that keeping her in her parents' home will cause her to be neglected or abused. Interviewing a 13 year old for 1.5 hours is more straining than 1.5 hours in a classroom, but most 13 year olds could handle it if the tone was professional. Not telling the parents where the child has been taken is required by operation of law in CPS cases, lest the parents "kidnap" their child out of state custody. So I am just being honest when I tell you that I do not see that any laws have been broken in that regard.
I am somewhat concerned about the manner of seizing the child; part of the problem may be that you were not present when the child was taken, but it is not clear to me that the police entered into the home to take the child. If the police actually entered into the home without permission, it would constitute a warrantless search and seizure and it would violate the civil rights of everyone involved. However, if they merely stood on the porch and said "the warrant and/or summons is on its way, so you better just do us all a favor and bring her out", there is no crime there.
Keep in mind that this system is supposedly to protect the kids who's parents are violent, careless drug abusers. They think that they are the good guys; play into that if you have to, but your focus needs to be on what needs to be done to get your granddaughter back.
I wish that I had better news for you, but I hope that my information helps.