My iPhone 4S is offline but I am connected to 3G and currently have service. Help?

I just had a scare where I left my phone on a bus but had it returned to me but I was unable to track my phone.

I had battery, service and even now I'm not able to track it right next to me.

Would really appreciate getting it working so I'm able to track it in the future.

I have tried removing the device from Find my iPhone and adding it again by signing in, this didn't do anything.

Would really appreciate some more suggestions! Thank you!