Items thrown through nether portals disappear if you quit before going through the portal

What happened in a single player survival game I threw different items through the nether portal then quit and reloaded the world and then went through the portal. On the other side, the items were gone.

If I throw the items through the portal and go through without quitting and reloading, then the items are there as expected.

I expected that after reloading and going through the portal, I would see the items I had thrown through the portal.