I think is misunderstood your question.
are you saying that there is no Random String binding in the bindings panel?
If so, you may need to create it manually.
Open the bindings panel, click the plus button and select Session Variable.
Name the binding:
if that does not stick, Close DW and use the OS file system browser to access the DW site root files and delete the _notes folder, then try again.
BTW: on looking at your site files, the webassist/email/templates folder has not been uploded