I'd say everything that reaches a filter has reached your mailbox, but I get what you're saying.

So I gather you're the type who checks the spam box for false positives? There's nothing wrong with that, and I know a lot of people do it. I tend to trust the GMail filters, never even look in the spam folder, and have the spam folder hidden under the "XX more" drop-down. I even have an extension in Firefox that, among other things, hides the count on the spam label.

The reason I've never bothered to do what you're trying to do is because of an annoyance in GMail search. For some reason that they don't explain, you can't do a partial word search in GMail like you can in the rest of Google. I find this extremely annoying. If I look at the spam mail I get, a good half of it has the word "viagra" in it, but it's always bunched up next to another word. I can't use something like "viagra*" to search for it. And these messages aren't even using cyrillic or something to try to get pass the filters.