What version of Thunderbird?

115.0.1

Were you asked to re enter your email account details when the program first started? Like as if it was a new install perhaps.

It would not open unless I put in my data, like a new install, yes.

I defer to Matt, but what probably happened is that Thunderbird created a new profile. If you look at c:\users\<yourid>\appdata\roaming\thunderbird\profiles, there are probably two profiles, the active one and the prior one with your addressbooks. The addressbook is named abook.sqlite (and there may be more than one with the basic name - they all comprise the addressbook). You can import them with the tools>import menu.