Have seen this about 5-6 times in last couple of weeks.
I have stacks of the 4 rare gems in my bag, anything from 20-100 of each type. I’m listing 4-5 of each type at a time on AH.
Sometimes when the expired (unsold) listings are collected from the mail it appears they REPLACE the stacks in my bag rather than being added to them. So if I have a stack of 90 rare haste gems in my bag and collect a stack of 5 rare haste gems from mail (from expired auction) then my bag is now showing only 5 rare haste gems in the bag slot where the 90 stack was, instead of 95 rare haste gems in that bag slot. Happens with all 4 of the rare gem types.
Then, within a day or so I get mail of more gems (not sure if this is just more AH listings expiring or a separate mail of the “lost” ones) and the missing ones appear back in my bag.
At first I thought I’d just accidentally listed 80-90 gems instead of just 5, but I’ve double checked this the last few times the problem happened and it’s definitely not the case. The “missing” gems are definitely not on the AH, in my bag, or needing collected from the mail. They completely vanish somewhere and then re-appear within a day or so.
Not sure if this is happening with any other items, but I’ve only noticed it with the 4 types of rare gem.
(edited to add latest occurrence)
It just happened again.
I had 20-90 missing gems of each of the 4 rare gem types and just got mail with expired AH listings being returned. I checked the numbers carefully, each returned stack was definitely only showing as 4 gems per stack as per the original listings, but when I actually collected them into my bags each stack included the previously missing gems and I got back to my stacks of up to 90 gems in my bag.
<edited again as the forum won’t let me add a new post>
I thought this was fixed as it hadn’t happened for a few days, but just noticed it again now. Gems collected from unsold auctions appear to REPLACE the stacks already in my bag, rather than adding to them.
I expect the missing ones from my bag to arrive back in the mail within the next day.