I personally conducted some tests by sending a text message to 466453 with my query and it responded okay. But many are still reporting issues.
The issues seemed to have started on the 20th, where some reported the issues were resolved a day later. But many are still saying they are not getting a response from Google's SMS search feature.
Maybe there are sporadic issues because one person not too far from me using the same network I am using says he is having issues with it. He said:
Same issues here in NJ with AT&T.... I sure wish we could receive an official status update from Google. Texting the word "help" to Google did not work either...
I rarely use SMS search because I have a smart phone but many folks still do use it.
Forum discussion at Google Web Search Help.