Every time I don't recognise the number

So I just got a call from a number I didn't recognise and I missed it. When I called back, it went straight to voice-mail.

Every time this happens I freak out, thinking that it is Adam calling. There are not many people who have my number (something I tend to be quite guarded about), but there are even fewer people who have my number and whose number I don't have. So, it is quite a novelty to get a phonecall from a number I don't have.

I will probably try calling again tomorrow. Or maybe I should wait until they call again? If it's someone who really wants to get in touch, then they'll just call back?

I DON'T KNOW WHAT TO DO!