Illegal plot sale on unregistered Power of Attorney

A plot of land located at Kollam District was reported to be sold under an Unregistered Power of Attorney obtained from my late mother at Mumbai in the year 1999.When asked as to who the purchaser was, evasive reply from the Attorney. Later due to misuse of the POA came to notice it was immediately cancelled in 2003. My mother expired in 2006 and then her properties were divided among the 4 heir as per order No 424/2012 issued by Kollam Civil Court now can we claim the plot sold illegally.