How long have you been going out with this girl?
You shouldn't have told her you miss her.
Listen you're playing right into her state. Whatever the cause is for that state, it's irrelevant to you. She has NO reason to still be pissed off at the ass grab. First of all it wasn't a big deal anyway. But on top of that you appologized. That incident is OVER.
Now, why was she off that night:
A) She was still pissed about the ass grab. If that's the case, you don't give a fvck, cus as I said, that's OVER. Nothing you can do about it, don't even think of bringing it up again.
B) You weren't in fun mode, but were in "apologetic" mode, which means you did everything possible to keep things smooth. That shows you care too much and you react to her, rather than bringing a good time out of your own self.
C) A million other reasons that have nothing to do with you. She had a bad day, she was tired, she's stressed, etc... You can't fix that, it's out of your control.
There's no "situation" to salvage. Girl's change their state all the time and they have very little memory for both the good and he bad. My ex once called me a horrible person, a terrible friend and an assh0le. The next night we were fvcking.
Take her to do something fun. If she's still weird, then she either she's weird, she's lost attraction or she's just not in a state to go out with you.
If that's the case just move on.
Oh, of course you "actually care" about her. You should care for all the girls you date, your FBs, your ex's and even your ONS. But trust me, there are oodles and oodles of girls out there that you can have a deep and fun relationships with. You're scared because you don't accept that there are. Seriously man, read posts here and you'll realize how common it is for us guys to get hooked on "that one girl". That comes from one of three things (or a combination):
1) What ppl call the "scarcity mentality". You blind yourself to the fact that there are tons of other women out there who are just as good or better than yours.
2) You haven't dated enough to realize that your woman isn't what you actually want in a woman.
3) You centered your life around her and once she's gone, you have nothing left. Don't ever do that. Keep a full life independent of your girl.