Why did I get a text message from an Unknown number?

So I have an iPhone 4 and I got a text message from an Unknown Number. Not a number that I don't know, it literally said "Unknown" where the number was supposed to be. There was no text in the message, and I responded with, "Hi, who's this?" and I got one of those error messages in return.

What does this mean? How do you even send a text message from a blocked number?

This is definitely interesting…

I doubt it's from a blocked number and I'd say it is safe to assume that this was just a text message that was corrupted some how on its way to you. It's really nothing to worry about.

Well you can't, but there are websites like anontxt.com that can send text messages to phone numbers anonymously.

If it was just a one time thing, I'd ignore it, I mean it's just like a freak thing. If it happens again, I'd call AT&T or Verizon and report what's going on.