But the alternative to "Scribd having the paper" is not necessarily "no other site having it". If someone uploaded it to Scribd, why wouldn't they upload it to some other site instead?
Your argument is equivalent to saying: the registrar of google.com is MarkMonitor, therefore if MarkMonitor didn't exist, we wouldn't have Google.
Your argument is equivalent to saying: the registrar of google.com is MarkMonitor, therefore if MarkMonitor didn't exist, we wouldn't have Google.