To send the webform you need the UCI or the Application Number, if you have not received the AOR you cannot have the application number, if you have a previous UCI of another type of application you may be able to send it, but they will not tell you if your package has arrived, I did it when I sent my application after two months without response and in their response they said that I should wait for the AOR.
What you can check is if the shipping service you used has the confirmation that it was delivered. We use Canada Post and they told us that the package was delivered two days after it was shipped. The AOR reached us seven months after we shipped the package.