Can you open the .qvw document in Qlikview Desktop in ADMIN mode? Or do you have a backup of the document that does not have section access? If the answer to both questions is no and you cannot find the password then you're out of luck and will have to recreate the document.
If you can open the document the first create a copy without section access and check that it can be reloaded by the Qlikview Server. Then put in the correct credentials of the service account for the Qlikview Distribution Service in the section access table and try again.
I'm sure you have a copy of the entries that are used in the Section Access table. Does Section Access of this document use the NTNAME field? Which accountname is listed in that field with ACCESS=ADMIN? Can you login into the server using that accountname? While logged in as service account, can you open the document in QV Desktop?
If the developer didn't use NTNAME to specify users that are allowed access to the document, then did the developer use fields USERID and PASSWORD? If so, was the service account also given access using USERID & PASSWORD (omg)? Did the developer use 1) the real AD password or 2) a custom password? If the answer is 2), your document is locked and you will probably never get in. If the answer is 1), enter the credentials in the Section Access fields of the Reload tab in QMC. There are special fields present to specify excpetional Section Access Username and passwords.