I believe that this issue is impacting both Single Player and Online play.
If you die, note very carefully where it is your body has fallen. Watch for landmarks, rocks, etc. Then, go back to that spot to try and recover your body. If your body is there - great. You’ve gotten your stuff back. If your body is not there, there is still hope. Your body is there - it’s just invisible as it’s not rendering on your client. I believe that Funcom has addressed this bug, and the patch is currently on TestLive. Some things to try for recovery of an invisible corpse container:
Invite a friend, and get that friend to join you at your death spot. See if your body renders for them.
E key spam the spot on the ground where you died. Despite you not being able to see your body container, it is there. If you E key in the correct spot, it will open your body container, and you can collect your things.
Try walking away from the area where you died, and then return. I don’t know the distance, exactly, but it needs to be far enough away to where the objects in that chunk will get unloaded from the client memory, so that they can re-load upon your return. One suggestion that I have read is to put down a bedroll, bracelet pull (die), respawn in the desert, bracelet pull again (die), and then chose your bedroll location. I have not actually performed this, but I have seen reports by others where this has worked.
Last resort: Get yourself a skinning knife, and spam the area where you died. If you cannot manage to find your body with the E key, spamming the ground with the skinning knife will destroy your corpse if you can hit it. Then, your inventory contents will pop into a loot bag. Just make sure you loot this quickly as the loot bag will not persist indefinitely.
Good luck recovering your stone tools and hemp.
Edit: Other note - the gravestone marker does not always accurately reflect the spot where you died. Just keep this in mind if it leads you astray.