There are several states where you can't recall a United States senator.
We have good recall laws in AZ.... looks like Missouri isn't so luckyhttp://ballotpedia.org/wiki/index.php/Laws_governing_recall_in_Missouri
Laws governing recall in Missouri
Missourians do not have the right of statewide recall. However, the right of local recall is available in:
Cities defined as Class 3 cities. A Class 3 City is defined as a city with a population between 3,000 and 29,999.
Cities that operate under their own city charter, if the specific city charter allows for recall.
The recall process that applies to Class 3 cities in Missouri is governed by MRS §77.650 and 78.260.
Recall may not commence during first 6 months in office
Grounds for recall must be stated, and must include misconduct in office, incompetence, and failure to perform duties prescribed by law.
60 days is allowed for collecting signatures.
Signatures equal to 25% of the registered voters in the city must be collected.