Caller: I don't know

Missed call. Thought I'd ask here first. Next, I'll call it from a phone box. Even if you put your phone on 'hide', they can still see your number.
Even some low-risk businesses have caller id software that this is child's play for. The end-user can't stop this and use cellphones, laptops, etc.. You can only minimise the risk.
I also thought I'd post this to make others aware.