missing photos

I've come across others who've asked this question and a variety of answers, but I'm quite incredulous at what I've found so I'm going to ask it again and see if what I've found is all there is...

I have an iPhoto library and it appears that a number of the items are "missing", which isn't the problem - the problem is that iPhoto seems to have no method of letting you know they're missing until you try to access one. That is there's no way to get it to just tag the missing items. This is a basic function of pretty much every other photo organizer application in existence. Trying to figure out which items in my collection are missing is exasperatingly tedious if I have to open each item.

Suggestions for a fix seem to vary from "try this script so-and-so wrote" to "buy this program". I'm quite shocked that the only apparently reliable way to deal with this issue is to purchase something extra from a third party. So again - my question is, is there a mechanism within iPhoto to indicate/tag items that iPhoto cannot find?

H.