Alright, so from what I see many people have experienced this bug. It's not the only one in SP right now, but I do think it is the one that's most annoying... and the only one that you can actually do stuff to avoid.
From my personal experience and what I've seen on the bugs thread, there are a couple symptoms that can help identify when a crash and loss of items is about to occurr:
- Weapon swap stops working
- You can't click nor move/remove any gear
- Using a potion on the belt will empty the slot, even if there are more potions above it on the same slot (and you might even be able to see them there)
- picking up an item and it not appearing on your inventory
If this happens, there are two things you should do IMMEDIATELY:
1) Go to the folder with your saves, right click on the save for the character that you are playing right now, go to "Properties", and set it as "Read Only" on the checkboxes at the bottom (uncheck it after opening the character again)
2) DO NOT SAVE & QUIT. Open your task manager (ctrl+shit+esc) and terminate the game.exe process.
If there has not been an autosave after the glitch, you'll be able to save your items.
If anyone detects any new early symptoms please share. Or if someone finds out specific events that can trigger the bug, please post it here so everyone can be aware.
Edit: I'll keep editing this post with contributed symptoms/triggers