Just go to google and type in the last little bit of the url.

Like.... say an image is uploaded to photobucket

Google search "Username/blablafolder/dudeimnotagirl.jpg" in quotes.

If the image was posted on a forum or something, it would be seen as plaintext and it would for the URL being posted in places. not the bbcode img tags.

Or heck, There may even be a feature in google image search for this exact thing.