That does sound like a great guess to me. I wonder if they will ever see this or do anything to correct it. I hope that they implement some sort of system to ensure that if items do poof… we can get them back. Game becomes not a game when your data randomly disappears. Well… maybe not so random in some cases.
Good job on this. Best guess I’ve heard so far.
Travel light out there travelers.
Seems like this happened to me as well. On a character full of runes (140 slots). All of it gone.
Well that’s strange…
Runes are simple items
https://user.xmission.com/~trevin/DiabloIIv1.09_Item_Format.shtml
https://github.com/krisives/d2s-format#items
It doesn’t take much information to describe them perfectly like with rare or crafted items. Also in our events, individual items are not saved correctly. It’s not that everything vanishes all at once.
Hi,
I want to give an update on this one. The d2s savefile limit really seems to be at the original value of 8192bytes (tested in singleplayer of D2R, see: https://ibb.co/ZBKj6Ps. Credit goes to Decay for testing).
Adding additional items on a character after reaching this value led to repeatedly losing items.
Thank you for the update. I’m going to wait it out till they put out a patch or some info that they are looking into it. I just can’t see playing, finding stuff and never knowing what’s going to vanish next.
Anyone know if todays update address the issues some of us are experiencing?
@devastation, it’s hard not to fill your stash when you play to magic find. 
Thank you to everyone who has replied. Hope they addressed or will address this issue soon.
Can someone notify me when this bug is fixed? /afk
Yep not playin noway, on poe atm o/
I also encountered this bug, personal stash was charms,rings,amulets almost all 1 slot items. The first time my tome / rings disappeared, the second time charms in my inventory but I had my recording software ready so I was able to capture the event from exiting my last game to joining a new one and the items disappearing, The d2s save file limit theory seems correct.
TheJudge as in TheJudge of Eve Online fame? 
Does anyone have any spesifics on the limitations to the save file? Is there a limit on the number of items, lines of text of the items or is there something else arbitrary that makes it impossible for us to find a safe amount to store in stash?
I wonder if something like this works:
https://web.archive.org/web/20160710044244/http://newd2event.net/index.php?id=methods/Bugged_Games_Dupe
Dupe methods always rely on rollbacks. So if anyone finds an exploit to crash a game that results in characters not being saved, yes.
But dupes are not the cause of vanishing items here.
Another victim here. Lost 20/20 sorc torch, 20/16/10 anni, life light gcs, life/res scs, gheeds after a long crafting session.
I am losing items also. I noticed when I join new games sometimes my Tomes will be missing and a few charms. I check my stash and iv lost many of my Unique rings too… What is causing my items to poof?
Save file overflow. Haven’t you read this thread?
Well I can confirm this happened to me now… I keep a spreadsheet of what items I have in which characters for tracking and I just lost M’vavina’s Embrace from my stash… what the hell… It wasn’t important to me but now I’m worried about my GG stuff…
I really liked the new patch! I logged in and filled my mule’s inventory. Save & exit. Then entered game again. Several items gone. Please tell me when next patch hits.
Another victim here, just lost my Ptorch. Diablo really needs to solve this issue.
Stop hoarding items. It’s a known bug so it’s on you to solve it till they patch it.