Creepy texts appear on iPhone?

I was texting my friend and put my phone face down on my dining room table, then I hear a beep from my iPhone 4s that I have never heard before, I pick up my phone and in the box where you are supposed to type next to the send button there were the words "Hello my name is Corey and I did before" some words were underlined in blue and I think they meant to say died before, but I did not write this and it appeared on my screen where you are supposed to type, it wasn't a message or anything and this happened again in the very same spot I put my phone down two days later, what could this possibly mean? I'm seriously freaked, did someone hack my phone?

Hard reset someone might of jailbroken without your knowledge and viewing everything you are doing.

Probably some hidden app running in the background… It happened to android phones with the girl from 'ring' showing up whenever you take a picture… Take it into the apple store and have them check it out… If you can't… Just reset your entire phone and you'll be fine.