DCF is a really problematic thing. I completely understand where you're coming from and we've had people close to us under false investigation from family services and it's a pretty bad gig. They act like everything you say is such an absurd lie and that you're just waiting for them to walk away so that you can start slamming your children into the floor again. It is really sad that they can't use common sense.
But at the same time, we've had people close to us exhibit a constant pattern of abuse with their children, including using and dealing hard drugs with the children present and leaving things like syringes lying around. We called DCFS and the investigation, as far as I know, has gone nowhere.
The woman still has her children because every time the agents show she happens not to have anything particularly incriminating in plain sight. The woman is a serial liar and manipulator and uses people wherever she can. She has many medical problems incidental of her drug use and the way she has treated her body and uses them to her benefit, playing the persecution card. We believe that she is constantly on the edge of sanity and has issues with schizophrenia. She is regularly beaten by her partners, and the children see this. She is always cracked out on legal prescription drugs, which she has a valid prescription to use, because as above, she has abused her body for years and now has serious problems as a result.
Her son has a disability that requires special attention. If he gets injured, he must be administered a booster immediately or he may die. This child is frequently unsupervised while his mother sleeps until 2pm and he runs around outside with kids who don't speak English, jumping off of balconies and stuff. He frequently misses school for a week or so at a time (she makes sure he appears at least once every 10 days, because the school people don't file a report until 10 consecutive absences). But apparently DCFS can't do anything unless they happen to appear at a time when the mother has drugs in reach or sight of the children, and the story is that heretofore they haven't seen this.
I sympathize that it sucks to be falsely investigated, but if you consider that there are people like those described above, who have become expert manipulators and liars to conceal and feed their habits, and DCFS has to investigate them too, you can understand some skepticism on the part of the agents.
Either way, it's a pretty horrible system. I don't really know the answer, but the current setup obviously doesn't work; this woman still has custody of her children six months later (the last time we had contact with them, her boyfriend, who speaks almost no English, called to say that the woman had been away for two days and asked us to take the children so he could go to work) and innocent people get harassed for years because of pettiness and retaliatory reports. Someone should try to fix this, though obviously it's a pretty intractable problem.