Items Vanish and Dont Come back

I was playing on my Survival World that i created today. I build a Nether Portal near my Chests. I did go to the Nether and made some Stuff Exploring etc. I died from an Enderman and Spawned at Spawn ~4000 Block away. So i tp myself to the Coords of the Chest. Then i got into the Nether and searched my Stuff. Then i explored the World for 20 Minutes and was annoyed so i used /locate Fortress to find a Nether Fortress. I then digged from the Netherportal to the Fortress and Ran out of Food. I walked back to the Portal and walked trough it to the Overworld and BAM My Stuff is Gone. The Chests were Invisible. But i right clicked them and they appeared but there was nothing in it. I dont now how i caused this Bug but it is annoying because i played the last 7 Hours in this Map (I dont have a Reallife)