Apps Disappeared from iTunes Library

I just noticed that the majority of my purchased and/or downloaded Apps have suddenly disappeared from my iTunes library. From what I can tell, the apps still exist on my various devices, but are missing from my library. I'm now scared to do a device sync, for fear that the apps (and all the accumulated data associated with them) will get wiped out completely.

Is there any way to pull the apps from my iPhone & iPad devices back into my iTunes library, without doing any damage?