alright maybe I am not the best person to judge this issue, but anyway, my friend is organising his 21st birthday party this Saturday, its kinda a last min thing but to say the truth I am a bit upset and disappointed with my another friend who can't attend

I give him the benefit of the doubt that he's really not free but at least he could have dropped by after his event since he says he will be free after 8 and we will probably be staying overnight at the birthday boy's house. but all he said was "nah I don't think I can make it", to say the truth, I don't know what he will be doing on Saturday but to totally turn down an invitation for 21st birthday without even considering? I don't know what to make of it really.