Can someone please help me understand what is going on with this command?

It works fine when i execute from selenium ide. However when i attempt to run using fitnesse, i get the following error:
Missing method: public TypeOfResult verifyElementIndex(Type1 arg1, Type2 arg2) { } in class com.neuri.webfixture.PlainSeleniumTest

I need to verify that an element is in a particular location in the list.