This is what happens with a valid parameter:
This is what happens an invalid parameter:
Note that the list of valid parameters explicitly mentions that "counter" is valid.
This is what happens when someone decides they want to "retire" a parameter, but only removes the use in the SQL query, and doesn't bother to change the input validation and help text to reflect that the parameter is not longer valid.
AKA, a mistake a first-year student would do, and a mistake a first-year student would find during rudimentary bug-testing.