You are right on the money - that is exactly what is happening!
I'm new to all this - it doesn't make sense to me that all the input in all the form fields is as it was upon returning but the layer (you are correct - initially hidden but then made visible by selection of a radio button) is not.

I've written some PHP code in other pages but not yet using cookies or session varibles - I guess it's time to start. Is there a specific variable that I should be looking at?
Thanks for your help.