Well, if you have no service at your friend's place, once you get back in range you're getting the messages that couldn't be delivered while out of service. It's like if you're in "airplane" mode; the device still works but it's not picking up any signals.
I had a problems with getting my text messages a while back. It wasn't a coverage issue, but I think something I'd downloaded. Unfortunately, the only way I could find to fix it was to hard reset and re-build my phone.
