(This content and subject are still fit, active,related, insightful for this one thread-topic instead of a new one up to this point)
I'm still mad about the Anime Tenchou x Touhou Project anime screening that was only shown at select theaters in Japan and never released outside of that, making it lost media. Done by ufotable and everything.
Yes it's been 14 years and I'm still mad about it.
I don't know how many people know about this but the artbook has been released online. Due to the forum rules I can't post the link (hosted on a very NSFW website), but if you google "アニメ店長×東方Project "artbook"" (make sure you keep the quotes on the word artbook) you will find it
Oh yeah I'm very aware of that and it's the only piece of media related to the anime itself that still remains out there and the closest thing we have.
Worst part is, I just remembered they did promise a DVD release in early 2011 or so but it just never came out ever.
Aghh.... curse trying to find Japanese media. Sometimes you'll be looking for something super specific and itll just be in one place hidden behind "SUPER OBVIOUS HENTAI SITE dot com"
Oh i just remembered. A user on another thread mentioned various doujin works that are very old and are the "first of X", like the first remix, the first fan-art etc. Among all of these, he mentioned a doujin comic called "The septentrion of the late princess" which was apparently the first fan-comic made about Touhou. It was allegedly published in 2002 at comiket 63. I wonder if people have already found this comic or if it's just another piece of lost media, because finding it would be a pretty significant event considering it's the earliest Touhou fan-comic ever made. There should be some kind of search party LOL 
https://www.shrinemaiden.com/index.php?topic=680.0 by around few days ago I have also searched. for, come across and posted for the good sake of that topic there, this one
https://pinky-cat.github.io/indexes/touhou-website-index.html, which is enough relatable and related to both threads-topics, and certainly o those persons-groups interested and/or involved or eventually so
There is also to highlight the rather important facts and details such as" the updating time is on the December 2024" together with"the inclusion of "multiple sources of languages, cultures, view-points, time-to-shift-to-insight periods... ".
Touhou Website Index
Updated: December 28th, 2024
The " Foreword(and related Front Page)" are as explanatory and as quoted follows...
"
Pinky's Cat Observatory
Personal
Writings
Indexes
Findings
Touhou Website Index
Updated: December 28th, 2024
As an index extension to Touhou Website Index
Foreword Awesome Touhou and to the wishes expressed in The Independent Web of 2hu - A Dream of Eastern Turnpikes, this index will catalog any parts of the web containing noteworthy Touhou content to act as a historical record. Feel free to contact me for any additions, comments, or suggestions to this list under the contacts listed under my Personal Page.
Table of Contents
... "
Post.Scriptum.
It is in not formatted through a visual-style and. but in a "more practical and essential Table-to-Link-to-Text-to-Label-to-Research'sstyle and format.