This question has been answered by BobRay. See the first response.
☆ A M B ☆
What do you mean by "the page didn't show in the sources tab anymore"?
The Articles resource is the container for the individual posts. The individual posts don't show in the Resource tree, they are managed from the grid in the Articles resource itself.
I haven't used Articles for years, never did like it, but I do know that much about it.
http://yoursite.com/manager/?a=resource/update&id=282
The first thing to try is deleting all files in the core/cache directory.
If you have upgraded MODX, also clear your browser cache and cookies.
If that doesn't work, take a look at the row in the modx_site_content table in the DB that contains your blog container.
Make sure it has a valid parent (typically 0), and is set to show in the tree. Make sure it has an alias. Click on the alias column header to sort the tree by alias and make sure there isn't another page with the same alias. Make a note of the resource's ID.
While you're there, repair all tables in the DB.
In the Manager, edit another resource. Edit the Browser's address bar so the URL ends with the resource ID for your blog container page (something like this) and press enter:
http://yoursite.com/manager/?a=resource/update&id=282
Does that bring up the blog management page?
Have you created any new permission rules since you last saw the page in the tree?
Thank you so much!!