Is it normal to still miss someone after them leaving 3 years ago?

When I was 13 I had my first girl - type of friend who I could speak to as any usual male friend at the time. We connected quite quickly, where we spoke more or less everyday for 2 years. Eventually, I begun to grow feelings towards her. I knew she didn't like me in that sort of way, which sort of made it easier to ignore them and move on (whilst carrying out how I normally speak to her).

One night, she messages me on my phone that she's moving town. Furious, I tried to ask her why she was leaving, but was turned down by her - unable to give me answer. She said a simple goodbye, summing up how we met - the stuff we went through, the ups and downs, and that we'd speak again one day.

It's been 3 years since and I'm still waiting for that day to happen. She deleted all of her contact info making it impossible to get a hold of her, no one knows why she left or where she's gone.

I can't seem to move on from all of this.

I'm 18 years old now. I've gotten taller, I've matured, I can look after myself, but here I am unable to let go of a dear friend where with the absence of her presence around me makes me realise how much I liked her without myself knowing.