How did they find me from my mobile number?

So my friend and i were messing around and there was this guy who had been quite rude to her, and i got his number (he 100% did not have my number).
I texted him and he replied saying "who is this?". I didn't reply and then like 15 mins later, he replied with a photo of me! (one of my old fb profile pics)
I have no idea how he got that from my number. My phone is an iphone and i believe his is aswell, but i still don't understand.

If you google your number, probably you'll reach your fb timeline, cause we usually link our numbers to our fbs.