I don't even remember how, but somehow I managed to make all of my project's source files hidden in Eclipse's Package and Project Explorer panels. Go figure.
'Show Filtered Children (alt+click)' temporarily reveals the files, and only in Package Explorer can I double-click to reopen them from this view. They go back into hiding after I select another item, though. Plus, now I'm getting other annoyances, such as all of the folded non-hidden trees altogether expanding when I click on any item, and the entire file folder tree of my project now being shown in these panels (including my .svn subversion folders... which shouldn't be any of Eclipse's business, presently).
Long story short, my Package/Project Explorers' just blew up on me, and I want to know how to fix this. Thanks in advance.