variable in URL after submitting form

variable in URL after submitting form

I have a form where I get a variable from the URL. kind of like /form/Proposal_ID=001
I created a script whereby if the form is accessed again with the same Proposal_ID there will be a message saying there is already an entry, and a link to see that entry. I also have part of the script an error message if the Proposal_ID is missing from the URL. When I first created the form, around October, things worked well, after a submission, people would see the first message and click on the link to see what they had entered. But around November, I found that after a submission people will see the second message, meaning that after submission, zoho does not detect the variable in the URL. Is this the case, or am I doing something wrong?