Gooru uses open educational resources (OER), which can be taken down by their owners without our knowledge. This is likely what happened to the resource you were using. You should still be able to view all of the other content for the topic you were studying or teaching by searching for the topic in the Gooru catalog.
One of the many benefits of OER is the ability to update and refresh instructional materials. Instructional teams and classroom teachers that implement new instructional materials convene regularly to review and assess the current resources, add new ones, and remove outdated or ineffective resources. Districts aggregate feedback from classroom teachers throughout the year. All of the information is used to evaluate and refresh resources.