When you decline an airdrop, does it go to recently deleted? When you airdrop a photo,  does it go to your recently deleted photos? I was wondering for a purpose.
If you are the Airdrop recipient and you decline to share with someone, it doesn't get saved on your system.  It simply isn't transferred to you. 

If you are the sender and the recipient declines your share, nothing happens; you still have the file and it stays in the same place.

If there's a file that you're seeing in the Trash (or as you mentioned it 'recently deleted'), that means the file was accepted and was then deleted.