Kurnmogh somewhat beat me to it re: timeline. A sibling asked me to put together an overview of the issue for reference, so I won’t post most of it here (just the pertinent parts).
P.S. I don’t know how to make real fancy posts beyond BBCode and using to insert extra spaces without showing anything. Apologies if it doesn’t come across all that cleanly, especially with the links as I didn’t want to take chances.
TIMELINE
2024-08-13
Patch 11.0.2 is released.
2024-08-14
Main bug report thread for issue posted by Vaelhaeyn-Wyrmrest Accord US. https://us.forums.blizzard.com/en/wow/t/guild-bank-missing-items-what-happened/1918643
2024-08-17
Support article created by Blizzard Entertainment acknowledging the issue, but no communication elsewhere.
2024-08-19
I added mention of the guild bank issue under “Known issues” on the “Patch 11.0.2 (undocumented changes)” page on Warcraft Wiki (WCW, formerly Wowpedia).
https://warcraft.wiki.gg/wiki/Patch_11.0.2_(undocumented_changes)#Known_issues
2024-08-18 — 2024-09-19
Other than an EU Customer Support rep that stated work was ongoing for the bug, there is absolute radio silence. https://eu.forums.blizzard.com/en/wow/t/guild-bank-items-gone/528709
2024-09-20
Support article unpublished. Update announcement posted to the US General Discussion and pinned by Linxy. Find out Blizz knew the cause just a couple days after (but chose to not say anything). And it turns out it’s not just a bug but outright data loss.
Restoration system mail sent out to guild masters several hours later. It doesn’t go well (soulbound BoE bags, items with no charges, etc.), with no communication about its problems.
Other than Linxy stating in a follow-up that it was fine to use guild banks, the update post remains the first and only time Blizz ever truly said anything on the topic.
2024-09-21
I added a section specific to the 11.0.2 problem to the “Guild bank” on WCW. https://warcraft.wiki.gg/wiki/Guild_bank#Patch_11.0.2_issue
2024-09-23
Bug thread quietly closed by Kaivax. Any new threads on the matter from this point on are moved and merged into the GD thread.
GD thread has become a support group basically. Preferred bug report thread as it attracted way less trolls though.
2024-10-05
Still no clarification to questions regarding the blue post itself, such as whether there will be any more restoration “waves” or that the rollout on Sept 20 was a one-and-done deal.
Still no confirmation from any player posts that any guild received everything back, or even a majority of what was lost. Everyone has been stating that they either received a minuscule amount or nothing at all.
2024-10-07
This thread is briefly unpinned from the top of GD forum.
2024-11-13
Thread renamed from “Guild Bank Missing Items Update” to “Guild Bank Missing Items Bug – Aug/Sept 2024” and moved from the General Discussion forum to Bug Report. Remains pinned.
News coverage remains sporadic. Only started picking up at the beginning of October, it seems.
2024-09-20
https://www.mmo-champion.com/content/12691-Guild-Bank-Missing-Items-Update-Complete-Restoration-Not-Possible
2024-09-21
https://gamerant.com/world-of-warcraft-guild-banks-items-missing-gone-war-within/ – very mid article
2024-09-23
https://massivelyop.com/2024/09/23/world-of-warcraft-data-loss-fiasco-deletes-items-out-of-guild-banks-and-blizzard-cant-fully-restore-them/
https://massivelyop.com/2024/09/26/massively-overthinking-do-you-expect-compensation-for-mmorpg-trainwrecks/ – follow-up opinion & thoughts
2024-09-27
https://blizzardwatch.com/2024/09/27/495-wow-guild-bank-bug/ – podcast segment lasted ~5min IIRC, very disappointing takes
2024-10-03
https://www.ign.com/articles/world-of-warcrafts-latest-expansion-wiped-out-some-guilds-inventories-seemingly-for-good-and-players-are-furious – Probably the best so far, surprisingly
https://www.dualshockers.com/world-of-warcraft-expansion-bug-wipes-guild-banks/
2024-10-04
https://hothardware.com/news/missing-items-in-world-of-warcraft – skimpy read, but whatdya expect from an obscure website 
2024-10-05
https://dotesports.com/wow/news/wow-players-from-72-year-old-vet-to-decades-spanning-guild-lost-their-gear-and-it-may-be-gone-for-good
https://boundingintocomics.com/video-games/blizzard-offers-minimal-recovery-to-world-of-warcraft-players-whose-guild-banks-were-empited-by-recent-glitch
2024-10-06
https://www.fragster.com/wow-error-frustrates-players-as-guild-banks-suddenly-become-empty