SetProperty question

I've been fixing bugs with the PDFThumb cookbook script I wrote
several years ago.  PDFThumb generates a thumbnail of a PDF file
and displays it with a caption and a link to the file.

The script implements two markups:  (:pdfthumb:) overrides global
parameters for the page, such as the size of the generated thumbnail.
(:pdf:) generates a thumbnail if it doesn't exist, and displays the
thumbnail with a link and caption.

In (:pdfthumb:) I used SetProperty to save the parameters for the
page.  It appears to me that key/value pairs are saved for the
specified pagename.  In (:pdf:) I use these values, if set, or the
default values.

I had thought that PageTextVar() retrieved the key/value pair for
the specified page, but that does not appear to be the case.

Do I understand SetProperty() correctly?  How are values supposed
to be retrieved?

-- 
Michael Eager