Maybe losing a friend

For the last almost four years I've called my friend Julie my best friend. Now for some reason she is no where to be found. She changed her number and hasn't contacted me whatsoever. It leaves me wondering if I did something to upset her or whatever. I don't know. Not to my knowledge I did, but could have. It's strange when I was in Virginia we talked almost everyday. She's lived in Phoemix all but five years in her life and ever since I moved here it's almost like we have nothing to do with each other, mostly on her end. I don't get it. Oh well, people come and go all the time right?