Most Helpful Girl
It could be many things.
The number could be wrong, either purposefully or accidentally.
They could have met someone they like better, in the time period from when they gave their number to when they were contacted.
They could be dealing with ex drama and just put off dating altogether, even though they thought they were ready.
And yes, people change their minds all the time, maybe they asked around about the person, etc.
I never give my number to anyone unless I really want to hear from them. However, I've known men and women to be guilty of the things I mentioned above. If someone acts interested and then doesn't respond, you're better off anyway. Who needs those games?