[[ PLEASE IGNORE THE POST, this is just to potentially help other folks, Moving the thing I was expecting to post to quote...]]
Game Version: 2.0.72.
Hey Folks, I believe I have had the same issue, let me see if I can explain the steps to reproduce. My steps are sligthly different than the OP, but I think the concept might be the same.
Steps to reproduce:
"Map out" to another planet.
Mark something to copy.
Open Blueprint Book, Look for a blueprint book you want to add this blueprint to.
Click (left click) on that blueprint, wrongly, instead of right click to open...
Realize your mistake and wrongly hit escape while holding the blueprint book wanted to add the BP to.
Puff, BP Book is gone.
Expected behaviour: BP Book should be dropped into either its original place, or the end of BP Library.
OMG: I'm stupid. I tried to repro and yes, the BP is on the character inventory, but when I realized my mistake (without noticing that it was in the character inventory, I quickly loaded a previous autosave, and the BP-book sync ensure that the BP-Library was wiped out, and cause I didn't had a save "post the fact" the BP-book that was in my inventory was lost forever.
This was a BP-book that I was collecting a lot of stuff I build on Gleba, but I only lost a few new additions, cause I manage to use "bypass library sync" to load a previous save, look at the bp library and recover the BP Book without the changes... Here's a write-up of a PSA after trying to troubleshooting this with Gemini, hope it helps others not make the same mistake as I did.
PSA: The "Panic Load" Can Permanently Delete Your Blueprints
I recently lost a heavily modified blueprint book due to a specific interaction between the Global Blueprint Library and the Save/Load system. If you use the Blueprint Library (B), read this to avoid the "Blueprint Void."
The Scenario (The Trap)
You are holding a blueprint book that lives in your "My Blueprints" (Global Library).
You accidentally "pick it up" into your hand (e.g., trying to reorganize or hitting Esc/Q while it's selected).
The book is now a physical item in your Character Inventory.
The Critical Moment: Because the book moved from the Library to your Inventory, the Global Library updates instantly to say: "This book is no longer in the library."
The Fatal Mistake: The "Panic Load"
If you realize the book is gone from your library and you immediately load an older autosave (without saving your current game), you create a paradox:
The Global Library is already updated to the "future" where the book was removed.
The Old Save is a "past" version where your character was not yet holding the book.
The Result: The book exists in neither the library nor your inventory. It is gone.
Why this happens
Factorio stores data in two different ways:
Save Files: Store your inventory, the map, and "Game Blueprints." These roll back when you load a save.
blueprint-storage-2.dat: This is a single, global file that stores "My Blueprints." It is independent of save files. It does not roll back when you load a game; it only moves forward.
How to avoid the "Blueprint Void"
Check your bags first: If a blueprint disappears from your library, it is almost certainly in your character’s inventory or the "Trash" slots.
Manual Backup: Regularly export your most important books as Blueprint Strings and save them in a text file.
The Emergency Fix: If this happens, Stop! Do not load a save. Go to %appdata%/Factorio and look for blueprint-storage-2-backup.dat. Copy it immediately before the game overwrites it.
The Hidden Setting: You can use the hidden Ctrl + Alt + Settings menu to enable bypass-library-sync. This forces the game to load the library snapshot that was stored inside your old save file, allowing you to recover the lost data.
PSA: The "Panic Load" Can Permanently Delete Your Blueprints