So in short:
My friend sent me a text
I never got it, but they got a response (that was not from me) that said "Sorry you have the wrong number".
My friend called me to see what the deal was. I said I never got your text in the first place.
Then I sent a text to them, they replied back and we were able to text from then on. They sent a screen shot of their text to me showing the message I never got and the strange reply of "Sorry you have the wrong number".
We had no history of texts before this (it had been a few years since we last chatted). What could possibly cause this to happen?