Google is changing its policy when it comes to My Drive's Trash. The Trash that you see on the left-side pane in Google Drive is your My Drive Trash.  

Google Drive’s My Drive trash will be automatically deleted after 30 days.

Also, please note files already in your trash will remain there for 30 days. After the 30-day-period, files that have been in the trash for longer than 30 days will begin to be automatically deleted.

A few more notes:

• These changes affect items that are trashed from any device and any platform.
• Files deleted from Drive for Desktop will be deleted from the trash after 30 days.

If you are using Google Drive on Android or iOS, please update your application to the latest version.