My xbox gamertag is "A Witty Retort".

A friend entered a nether portal, quickly followed by me. The screen went to building terrain, and while it did, it made the hit sound continually. It never loaded the terrain. My friend got the notification that I had died, and none of my things were on either side of the portal. The terrain never loaded and I had to turn off my xbox.

When I respanwned at my last spawn point after rebooting, I had none of my items, and they were not dropped on either side of the nether portal. 

Important items lost, I would hope could get replaced:

A diamond pickaxe with Efficiency 4, Unbreaking 3, Fortune 3 and Mending

A  diamond shovel with efficiency 3, unbreaking 3, and mending

A diamond sword with Smite 4 and mending

diamond boots with feather falling 4

And a shulker box which had fairly easily replaceable contents