I'd also point out that unless your passwords are store in some predictably-structured file format, it may be pretty difficult to tell that it's a password even if they hunt through the bits. Things like JPEGs are generally pretty easy to recover, but arbitrary text files? Not so much, if you don't know what you're looking for in the first place.
On a side note, I'd presume structured data like credit card numbers could potentially be found, even if there were false positives, no?