Thread moved to the Carrier Discussion forum
BTW, I have the same issue. Sprint has been known to regularly block short-code numbers that are sending numerous text messages to your phone. From what I've heard, the system marks them as spam after a certain amount and blocks them.
I had that issue with Chase Bank text message alerts, so I called Sprint. They said the number was on the blocklist, they had to white-list it for me to get more messages from them.
The problem with Facebook is, however, that they use multiple numbers to send alerts.