Suffocation in Nether Portal and losing items

So, I was playing with a bunch of my friends and I went to the nether. I returned to the overworld with a bunch of cool stuff like wither skulls and diamonds. During the “generating terrain” of whatever thing pops up, it takes quiet a while, longer than usual. I assumed it was my lag, so I just waited UNTIL I HEARD my character getting damaged. I was panicking, because this has happened to me a few times before but this time, is even worse. Obviously, I died. But that’s not the point; I went back to the portal and my stuff were all gone. I went into the nether again and it wasn’t there too. The portal was placed in a wall. Please look into this, Mojang. I was really upset.