hello mate
saint it right..that was a pretty afc move...its ok it is not the hardest thing to fix
i myself..sadly did the same thing. met a girl and got her name, talked for a little bit and i ended up being stupid and not having the stones to ask for her number facebook found her. did the same message thing...it didnt work at first but slowly it did..ok here is my advice, based on what i did
now i sent a message pretty similar, just a typical hey convo starter..not too good. now, what you should do is send one more, this time i suggest to just go direct..it is a little ballsy but hey it most likely will work. i did something along the lines of
"hey it was great meeting you the other day i enjoyed talkin you are really laid back concidering i had just met you! im gonna be completly honest i really wanted to ask you to go out for a bit to eat and just get to know you more but i was in a little bit of a rush and work was on my mind and i missed a great chance to hang out with a cool girl. (well so far you seem cool but hey i might be wrong
) i really hate facebook chats but i just wanted to contact you for the sake of meeting up again and figured you might not be strolling in when im working. it would be great to go out for a coffee this weekend. i normally dont trust random girls with my number but...you did make my shitty work day a bit better so il trust you for now 
555-3849..."this is just very fast off the top of my head what i would do. now, i gave compliments to show that im not weird. making the convo good with smily faces and exlamation points although sounds gay make it less weird, like you are KINDA expressing some emotion. also, saying that you are honest is also good, cause this will make her flattered that you are being bold, but also show her you arnt creepy, what creeper stats an honest thought to a girl? WITHOUT it being rude and sexual? you get the point. another good thing is to say you dont like facebook chattin. it shows you have a life besides the internet, and that you arnt gonna keep messaging her all the time. the funy little trust and the number is something i add alot when i meet girls, its just a fun way to give or recieve a number.
now dont do this word for word, but the basics i described should be put in there. you want to come across as a real person who just thought she made your day and is worth hangin out with later to talk
some guys might not like this, but i did almost this EXACT type of message and it works just fine, after this though just dont send her any more shit, she will call or leave her number, then dont do any more weird shitt
mR.e