Site rolled back a year after update to 5.2.2

I updated to version 5.2.2 today. The update went well. No error messages. It asked me to upgrade the database, which also went well. All seemed fine at first. I can navigate around the site, update themes etc. No problem. All themes and plugins have been updated.

However, I realised that the theme I was using was gone and the site had reverted back to the previous one. That in itself was not an issue.

I also noticed that a plugin I no longer use was now active and was asking to be updated, even though I thought I had disabled and deleted it.

Then I noticed that all the posts I’ve made over the past 12 months are also gone. Everything appears to be fine, except for this step back in time issue. I couldn’t find any posts in the support forum where the same thing has happened to other sites. Is this something I should be concerned about? Can anyone tell me if the data would still be in the database but inaccessible for some reason? Can it be fixed or do I have to restore a backup?

Any help would be greatly appreciated.

Thank you.

The page I need help with: [log in to see the link]