I wanted to edit the index.html file that sits in the ~/Sites folder. If you double-click this file, Explorer opens. So I picked it up and dropped it on my jEdit icon in DragThing. Poof - the file vanished! jEdit is a Java-based text editor, not some kind of auto-deleter, so it looked like there was a bit of a problem. A quick look showed it wasn't in the trash, and I couldn't use Sherlock to find the file, since I have about 2,500 index.html's on my machine ... so it had basically vanished into thin air.
As an experiment, I duplicated a text document, renamed it to "XXXYYYZZZ" and dropped that onto jEdit. Same results - poof, file's gone. But this time I launched Sherlock, and searched for the file. No sign of it on any disk. So once more, I went back to the finder, duplicated a text file, and named it the same thing as before. Dragged it onto jEdit, but this time, I got a message about there already being a file with that name in the location, and did I want to rename the file?
This was the enlightenment I needed. I went to the finder, right-clicked on the jEdit app, and chose Show Package Contents. There, sitting inside the jEdit application bundle, were all my test files, and the missing index.html file! Somehow, dragging and dropping the document on jEdit moved it into the app bundle, instead of launching jEdit.
I tested this with a couple other apps, and couldn't repeat the behavior. But I can repeat it consistently with jEdit. So if you use DragThing, and you seem to have dropped a file and had it vanish, check the bundle for the application you dropped it onto -- it may very well be there!
Mac OS X Hints
http://hints.macworld.com/article.php?story=2001040301440533