My brother was only 4 months old when he was adopted. He was in an orphanage and didn't get much attention. He had severe bonding issues... even at 4 months.... by the age of two he was diagnosed with Attachment Disorder, very common among adopted infants and children. So the fact this child wants and needs to be held is good.
So yes, an infant in an unstable home that was removed will likely have neglect issues from that, then is moved to foster than another home, it is going to take a lot of time due to the instability, dedication and a lot of holding and caring. Especially if it is a drug baby. Even then there may be long term bonding issues. The program should have some information regarding this. This is likely not an issue the foster parents created.
I agree, co-sleep with this child if possible, or at least room with it, give it lots of close face time, stay home with it and create a very stable environment, like don't pass the baby around to visitors or have other babysitters and caregivers. You don't say how old the child is, but if it's still young enough, child wearing in a sling may be very helpful as well.
This could also be another issue entirely, such as reflux or reaction to formula change. So be sure the baby is checked for that.
This couple should get a book or join a support for adopting babies. There is a lot of information out there.