Did they get my text on iPhone 4S?

I sent a text to other people on my iPhone and it says delivered and they all replied. I sent a text to my other friend and it said sent as text message and he didn't reply. Does that mean he didn't get the text? He has an iPhone too and we both have the iOS 6 update.

He probably missed your text. Just wait.

Could be that he has his iMessage off, has his phone off/airplane mode, has no phone internet(3G, 4G, etc,) no Wi-Fi available, or does not have any phone signal where he's at.

iMessage requires an internet connection, mobile data or Wi-Fi, in order to work.