Dfs determines mother unfit; judge doesnt research and grants custody:grounds for lawsuit?

division of family services determines mother unfit and takes children (4). (3) are placed with her famiily members and (1) placed with the father (children have different fathers). mother files pfa against father with custody of one child, requesting custody as part of it, and judge immediately grants it. 6 days later in court, pfa dismissed because no evidence to support. child still not returned to father. child placed in foster care for approx 4 months and slowly increased visitations with father. now child placed BACK with father (where child originally was) and pending custody hearing. father is now required to take cles/courses due to ALLEGATIONS that have not been proven true with NO financial istance (father has four other children to support with no financial help). question is can we sue state that issued the pfa without researching a little first or is it the judge personally or do we not have a case? (this is the very shorthand/general version)