Grandparents rights when parent leaves the state and children are being neglected?

Here is the situation: My mother lives in Florida and, until recently, my younger sister and her two children lived there too. My mother would have the children 5 days a week, and during the evenings and overnight on weekend. (so yeah, basically all the time) My sister was never really concerned about it because she was able to go out, work (sometimes) and try to keep an eye on her "husband". Well, her "husband" up and left for Joplin, Missouri (yep, same place on TV now) and my sister became lonely and thought that if she brought the kids to Missouri, the "husband" would have no choice but to come back to her. So, the Saturday before that eadly tornado went through Joplin, she tells my mother she will watch the children. Of course, she actually just takes off with the kids and steals one of my mother's cars in the process. (Let's also add into the note that my mother was IN THE PROCESS of trying to get custody of both children!) My mother was scared that if she reported the car stolen, the children would be put into the system and she would never get custody of them. Anyway, my sister goes to Joplin,Missour and we all know what happened next. Now she is trying to ask my mother for money and such, using the sob storey that "the baby doesn't have this" or "the baby doesn't have that" (one child is a 6 year old boy, the other is a 7 month old girl) but she has money to try and convince the children's father to come over. (She basically pays him to come and see them). My mother has offered to have the children flown back but my sister wants none of it because she "knows that eventually the father will come around." The children are sleeping in a car every now and then because the father's side of the family wants nothing to do with any one of them and my sister has only 3 sets of clothing for them. She says she would rather make this sacrifice than try to live without this man. She has left the children at shelters with people because she "was checking into work" at late hours (we are talking midnight and on) and sees nothing wrong with the children just being shuffled around. She wants my mother to take pictures of things in Florida and send it to her so she can claim that she lost those items in the tornado, ie a television, a different car, expensive stuff you know). She is impossible to track because of the hopping she does from shelter to shelter, but we do know she is still in Joplin. The CPS in Missouri is very busy now, understandably, but there has to be something that can be done. I am unfamiliar with Florida law (I work in law enforcement in Texas) and have no clue of what else to do. We have tried contacting CPS in Missouri, but they are very busy; the social worker in Florida says there is very little they can do right now. There must be something to expose the fraud she is trying to pull and the way she is neglecting these children. Any SERIOUS advice would be appreciated.