Yes I had this situation once and I don't know if that was the right way to handle it but it worked for us. We would call Mum and Mum reassured the child their sibling was ok and that settled him. With the other children in care I would get him to help call everyone inside and help me count that everyone was there.
After a while of doing that he felt safe and assured that everyone was alright and it settled down.
In saying that though any new situation that the Mum encountered it would flare up again but I had no more problems in care.