Call from a strange 00000 number

Have you ever received a call from a number that was a bunch of zeros??? I looked it up online and the majority of the responses said it was an illegal number. Perhaps from skype or another internet phone. Could be a scam. Obviously, it's best never to answer calls from unknown numbers but someone in the house, who didn't know better, did. They only said hello, and there was silence. Later in the evening I tried to make an international call and it wouldn't go through, a first. Anyone else ever have this happen?

Usually VOIP type phones (Skype, etc.) will display a 000000 on the call display if they don't have a number assigned to them.

hmm, come to think of it, the phone said we had a voice message, which we don't know how to retrieve yet. Why it didn't roll over to our regular answering machine, idk. There's plenty of people we know that use internet phones down here. This was a first to come up all zeros.