am i overreacting- bf flirting on fb?

my bf and i are long distance. he gave me his fb password a long time ago.

today via Skype.. i caught him smiling from ear to ear and looking at some girl's fb profile pics.

so i read their conversation and it was some girl he knew from years back (he's moved far away since then). and she kept calling him "soooo cute and handsome". he wasn't really flirting back besides telling her she looks nice but he did say one thing... "you should have told me you thought i was cute.. we could have had some fun before i left!!"

am i overreacting? i know he'll never see her again in his life.. and that she's literally no body in his life.. am i overreacting about what he said?