Help Posten missing package

Hey wonderful people, I sent some documents from Oslo to Stockholm on 27.2 but the receiver says they’ve never got it, it’s been almost two weeks now, I made a grave mistake of sending it via normal courier without tracking(a blunder from my end) I’d like to know if there’s anyway of knowing if the package has been delivered.

I still have the receipt, I walked in posten office to check if they can help me in any sorts unfortunately they say they don’t have any information nor do anything to help me.

Any advice tips will be really helpful. (I did learn my lesson and never going to send anything without tracking )