Family Sharing: Update Ticket / Request Share

[zeroCat]

Sometimes, Steam will (for reasons unknown to me) forget that you have access to another persons shared Library. All games borrowed from them and not installed will disappear from your Library. Those that are installed will have a <Borrow> button instead of a <Play> button.
When clicking borrow, a loading window will pop up saying "Updating Ticket..."
Then, a gui with 3 buttons opens, saying

"This game belongs to Steam user ... Would you like to request access to ... games on this device?"
[Request Access] [I'd rather buy it] [Cancel]

When then pressing [Request Access], steam will realize that you are already authorized and say
"We've discovered the owner has already authorized this device for game sharing. You're all set."

How does this work? I believe that this happens when the steam config.vdf is missing the sharing token of the account that shares their games to you.
This GUI is probably ment to open when your User Account is authorized for Sharing, but your Guardian File is not.
The Steam Client only seems to offer this if you already have a game of the sharing person installed - if you do not, there doesn't seem to be a way via the Steam GUI to do this, and you will have to bother the person sharing their games with you to do the entire process of family sharing again. It's probably still possible via the api though, which is why I want to make a little program to recover the Sharing Tokens. For this i need the API functions that the GUI described above uses.
Is this implemented in the API, or could you please implement it?
Thanks for all your time on this project, i really appreciate it and will try to make useful tools with it!
- some random thankful user

[Dr. McKay]

Sorry, I've really only done a minimal amount of research into how family sharing works, but off-hand I don't remember any way to retrieve an authorized-device token from Steam. I guess it must be possible considering that flow you're mentioning, but I don't know how it works.

[zeroCat]

Alright. Do you still plan to eventually implement this, or how would one go about finding and implementing these requests themselves?

[Dr. McKay]

I honestly doubt I'll put much more work into family sharing in the near or semi-near future. You might be able to use NetHook to see what traffic the Steam client sends during the events you're describing.