How can I find my threads in Apple Support Communities?

Tap/click your name at the top left of this page, and select “My Subscriptions”. There you can select the “Filter” section and further select under recent activity: “Participated” or “Authored”.

This one: Time Machine Back Up - Apple Community

Did anyone respond to your thread? If yes, check your emails from that date.

You can change how the forum communicates with you by tapping your user name, then preferences and turn on notifications.