thomas cain 's mother orae mae died in 1943 , when he was just 13 .
he thought that no photographs of her had survived .
granddaughter andrea ferrell , 29 , tracked one down , and filmed the reveal .
emotional mr cain sheds tears as he looks on image from the 1920s .
ferrell is now looking for other photos - especially mr cain 's father .
can you help andrea ferrell track down the photograph of her great-grandfather , henry cain ? email her at andreavferrell@gmail.com .