Because SharePoint Designer caches what it thinks the site's contents look like, sometimes, this cache gets out of date with reality and you will see issues when SPD thinks you have some files checked out, but you don't.
And in the past, I would go and Bing and search "clear SharePoint Designer cache" and this will net you:
- http://www.myspblog.com/2011/07/clear-sharepoint-designer-cache.html (pointing to)
- http://spandps.com/2010/10/13/clearing-the-sharepoint-designer-2010-cache/ (which points to)
- http://www.hexanes.com/?p=558 (and points to)
- http://urbandude.com/post/2007/04/02/Sharepoint-Designer-web-cache-issue-fix.aspx (404)
So there's no shortage of finding the command to clear the folder.
I came across this part of the SPD UI by accident.
- Select Home in the current site.
- Go to Site Options.
- Select Advanced Tab
- Click Delete Files (temporary files)
You will see that any currently Opened Folders views will be empty.
As the cache for the site has been dumped. You need to refresh from the Ribbon Bar and you'll see the status of the items has updated correctly.
SharePoint Designer 2013
The same UI exists for SharePoint Designer 2013 as well.
No more command line, perhaps.
Let me know in the comments if this was something you've ALWAYS known about, or whether it also made you feel foolish that you've been using the command-line or deleting cryptic user profile temporary folders for years, literally. When there's a button that does this for me.