The only way you can retrieve a deleted post on your Tumblr blog is by restoring the original post from a backup copy. You can back up the HTML code for the post manually, or use a backup tool like Tumblog Backup Jammy to make regular backups of the HTML code of all your posts at one time.
Manual Post Backup
To manually back up one of your Tumblr posts, open the post, click the gear icon, and then select “Edit” in the menu that displays to open the post in Edit mode. Click the “<html>” icon to view the HTML code, select and copy the HTML code, and then paste the code in a blank text file. You can back up several posts in a single text file. Store the backed up posts in a folder labeled with the date of the backups.
Mass Post Backup
There are only a few tools are available that enable you to back up several Tumblr posts at one time. The Backup Jammy tool extracts the HTML for up to 500 posts at one time, then stores the code in a compressed text file with the ZIP file extension (see Resources). Though backing up your posts using Jammy can be quite cumbersome if you have several pages of posts, using the tool is much more convenient than performing manual post backups.
Restore Backed Up Post
To restore a backed up post, open the text file containing the HTML code backups, launch the “Find” tool in the text editor, and then search for a word in the title or content in the post to restore. Select the HTML code for the post, and then copy the code to your clipboard. Open Tumblr, and then click the icon for the post type of the original post. Select the “<html>” icon to open the post’s code view, paste the HTML code in the post form, and then click “Post.” The original post is replicated in your timeline.
The Tumblr platform automatically backs up 20 versions of your theme, so if you accidentally delete portions of your theme or make changes that break other features, you can quickly restore the theme to a prior state using the Tumblr Theme Recovery tool. Log in to your blog, and then browse to the Theme Recover page (link in Resources). The last 20 theme revisions are listed on the tool page, and a date and change log is provided for each revision. Click the “See Changes” link to view the changes made for a particular entry. To restore the theme to an earlier version, click the “Revert” button in the entry for the version. The selected version is immediately restored.