My guess would be you know the answer already, but find it difficult to accept it because it isn't the answer you want to hear. Although something could have happened to her, it is more likely she isn't that into you, and you have better things to do than bang your head against a wall trying to get her attention. There was an episode of "Six Feet Under" where Rico is really into this girl, and he calls and calls, and she never gets back to him. He thinks something terrible has happened to her, and goes to her apartment, finally, and gets the landlady to let him in. Out she comes from the other room, and when he says how worried he was, she blithely goes "I didn't respond to you because I thought you'd get the hint." LDR's are notoriously impossible anyway, unless both parties are willing to keep in touch beyond the norm or someone is willing to move. Good luck, and there are more fish in the sea who would appreciate you more than this girl is.