Ok, the handle appears to be hidden.
This thread got me on the right path
http://uk.mathworks.com/matlabcentral/newsreader/view_thread/313495
I found the handle by using the following:
findall(0,'Type','Figure','Name','N-way ANOVA','HandleVisibility','callback')
and was able to change the HandleVisibility to 'on' so additional plots using this function would not be picked up by the findall command