>WordPress automatically upgraded all my client’s websites wppizza plugin
no, wordpress does not do that . but other plugins, themes or custom scripting might

For over a year now – there was a notice in the wppizza plugin warning people about NOT to simply update the plugin when version 3 comes out. Then – when version 3 was made available – the warning got even bigger and redder. (Not to mention that it is also clearly said in the changelog) As well as a link to the upgrade instructions

Don’t get me wrong, I can understand why people do autoupdates and up to a point they have their merit – if updates are updates for micro or perhaps even minor version changes. Autoupdating major versions however is simply a very bad idea. This is not only the case for wppizza but for any plugin or theme.

Back to the issue at hand though:
Other than restoring a backup , there isn’t any way back from 3.x to 2.x
however, you can try re-saving each of your settings pages to start off with, also enable debug and check your debug.log file

i would first of all recommend to at lest read the upgrade instructions once or twice