I just bought the phone off craigslist and now the external speaker doesn't make a sound. Not a peep. I called tech support and they offered to replace the phone under warranty as long as it isn't rooted.

How do I know if I'm rooted. There is nothing on the start screen except for the nexus X. The rep I spoke to told me that there are ways to hide the yellow lock or key or whatever it is.

Before I bite the bullet and send it in I just want to be sure that I'm not going to get slapped with a "Sorry, the phone has been rooted your warranty is void".

Any help?