Should I be worried about him going back to her?

Okay so, when my current boyfriend was dating this girl. We were pretty close friends and stuff. He told me like what he was gonna get her for her birthday and those special days. But then they broke up and she moved.. i don't really know why they broke up. But on facebook and stuff she will post on his wall like "Adam, I miss you so much. When I come down this summer we have to hang out. love you." And like will comment on his pictures and say like you're such a cutie(: so i asked him the other day if summer ever told him that she liked him if he would go back to her? he said "nah" and i mean to me that's not like a real complete answer. I mean I might be over exaggerating or something, but i just wanna know if I should be worrying about this or what...