Lost iPhone 5s, Find my iPhone shows as being offline?

A few days ago, I lost my iPhone and am quite sure that it was taken by someone. When I noticed at home, just about 20-30 minutes after, I checked Find my iPhone online and the phone showed as being offline. I turned on lost mode and sent the loud sound that is still pending as of right now. I just recently read that if the phone was online in the past 24 hours, you would be able to get a location on it but this is not my case... so this is leading me to question if in fact it is the application that is being blocked somewhere instead of the phone being turned off? But then again, when you call, the phone appears as to be completely off.

Thoughts? Suggestions?