Upon mobile restart, when I clicked on Diarium app, it popped the message that I'm on trial version. All my entries were gone! I went to Google play to check if I was on the same ID in which I had installed the Diarium app and I was. When I could not recover my entries, I uninstalled the Diarium app and reinstalled it. But with no hope. The data is lost.
No, I have not cloud synced and I'm not using this app on any other device other than the one I installed initially [Samsung zflip].