So my phone recently has been sending messages as text instead of iMessage. When this happens, on very few occasions, the message does not go through. I texted this girl to hangout and just my luck, it sent as text message. I was worried she didn't get it and ended up texting her again about 2 hours later. She responded after the second text and just out of curiosity I asked her if she had received the first one. She had. Moral of the story: never double text, always assume the message was delivered. If it really did go through, you come off as needy. If it didn't, oh well, act as if she hadn't responded.