The message seems to have gotten sent since it's in my Sent folder rather than the Outbox. Fluke? Something going on on your end? Hopefully it's a one-time event. Sending fuel-ups via text messages is pretty convenient.
Extra entry? So it worked the first time around too?
SMS can be tricky, especially if you're moving in and out of coverage. So it could have just happened to land in your outbox but was still in transit before it hit the Fuelly SMS server.
No, the extra entry due to my going to the website and adding the fuel-up manually (after it failed to work and before my post here), followed by testing it again due to your suggestion when it worked.