There are many plugins in the WordPress market that use the posts table to store temporary or segmented data, this is because WordPress does not supports the creation of separated tables to process data independently, plugin/theme developers usually hook the predefined WordPress functions to insert their data in the same table as the posts and pages but set a flag in one of the columns to differentiate them so they do not appear in the normal interfaces, but they still appear as “posts” in the actions triggered by WordPress and monitored by the plugin, so for example, if one of those plugins is creating a temporary entry in the posts table (like contact form or feedback plugins do) they will appear and dissapear in the audit logs like you saw. Please check the “Ignore Alerts” in the plugin’ settings page to disable the alerts for specific post-types like this one.
