Newborn Placement

My husband and I took placement of a newborn five weeks ago. The newborn is a biological sister to our FD. We are adopting our FD in a couple months. Baby was born addicted to meth and opiates. The meconium test positive at our local hospital but once it got to the "big" lab it tested negative. Our pediatrician's office has it in their records that the baby tested positive. The baby has showed many signs of withdrawal. We got a call a couple days ago stating since mom tested negative for drugs and has been clean for six months and can prove it we have to give the baby back to her bc dcs has no signs of endangerment. Our FD big sis was removed and tested positive for drugs when she was born also. So bio mom has substance abuse. I am so worried sick for this baby. I didn't know if anyone had a story similar to ours with a little hope in the future. I know this baby will be back into care but it just a matter of time but it is killing me.