I believe that my sister filed for a lost vehicle title so that she could give my mother's car away.?

My mother suffers from severe dementia. She lived with my sister for a while and just before she was placed in a nursing home my sister gave my mother's car away to her daughter. I believe she filed for a lost vehicle title so that she could do this without coming to me for the title. The title is not lost. I have it along with my mother's other legal doents. Is this fraud? How do I find out it she did indeed misrepresent the truth?