If it was the Postal Service you can request a copy of that signature. (Just in case you didn't already know this). I would send a copy of that to the person who was supposed to receive it. Also, please contact your Postmaster or the Supervisor of the delivery unit. It should be reported.
I have seen situations where one member of the family picked up a package and forgot to tell their spouse it came.
They might leave it somewhere say in their vehicle for example and forget about it. In your case if there was someone at the home that received it, they may have put it somewhere and the person who was supposed to receive it doesn't know it's there...(just thinking through possibilities)... Hope this helps