https://sos.oregon.gov/voting/Pages/instructions-disabilitie...

   Step 4: Return your Ballot

   After printing your marked ballot summary:  
   Enclose your ballot in the secrecy envelope.  
   Then place that envelope in the return identification envelope.
   Sign the ballot declaration and the return identification envelope

Is your theory simply that nobody in the Oregon Secretary of State's office thought people might try to cheat?