Without more knowledge of 'Taken Back: Finding Haley - True Story', it's hard to say exactly who the main characters are. However, if it's a true story about finding Haley, it's reasonable to think that the people closest to her, like her family or closest friends, would be main characters. There may also be some authority figures such as the police if they are involved in the search process. And of course, Haley herself, who may have her own story and reasons for whatever situation led to the need to be found.
Given that it's a story about finding Haley, she is likely a main character. Then there could be those directly involved in the search. Maybe it's her parents, who are desperate to find their daughter. There could also be some helpful or hindering side characters. For instance, a neighbor who saw something the night Haley disappeared and could be a key to the mystery, or a person who tries to mislead the searchers for some personal reason.