How is that possible? Did they change how Steam's offline mode is enabled? For years you have always had to be ONLINE in order to enable offline mode. So in that case if your connection goes down you are shit out of luck since you can't get online to go offline. This has been a big bitch about Steam's offline mode for years.
i don't know if this was ever different. i sure as hell never noticed that they changed it.
i do know, however, that you need to prepare offline mode in advance. maybe that's what you mean. you have to have started each game you'd like to play in offline mode in online mode first, sort of like a verification. you also have to save your login credentials locally.
like i said, i found myself forced to use offline mode several times since February and it has always worked flawlessly.
Offline mode works BUT if your going to be offline for any length of time, there is no way to know when you have to go back online to 'reauthenticate' your credentials then go back offline. I know.I asked Steam support and they weren't able to give me an answer on exactly how long you could stay offline for (days/weeks/months???).
AFAIK there are no reports anywhere that this is actually necessary. there are people who claim they've had Steam running offline (on a laptop, for example) for years and never once had to re-authenticate.
as far as i know, the re-authentication story is a fabrication.