Go to the scene where Aj is running out of his room after Harry sees his daughter. AJ throws boots on his shoulder, a few scenes later after Harry shoots at AJ the boots are on his feet but we never see him bend down to put them on or anything.
We didn't see Grace (Liv Tyler) take off her Bra either but yet we see Harry (Bruce Willis) find it in a "taken off" state.... The point is just because we don't see it, doesn't mean it didn't happen. In a movie, some things are just meant to be "given" as having happened. That is, the movie went for what? 2.5 hours? but the time throughout the movie was portrayed as being something like 1 week! I'm sure lots happened that we didn't actually see! :P