Structural search help

I'm trying to find all occurrences of a certain log4j logging call. The call
looks like logger.error("somestring", anObjectOfTypeThrowable).

Of course the logger variable could have any name but is always a
org.apache.log4j.Logger. Same goes for anObjectOfTypeThrowable. And the
string could be a variable instead of a String literal.

My current template is $logger$.error($string$, $exception$) with the logger
variable Text constraint set to Logger, the string variable set to String
and the exception variable set to Exception. The Logger and Exception
variables both have the "Apply constraint within type hierarchy" selection.
It doesn't find anything when I know there are a lot of them. What am I
doing wrong?