I've done a couple of updates to my magic trick app, 5 Card Trick.
Both times, I couldn't see it in iTunes when listing by category and release date - but it shows up fine if I do a search for 5 Card Trick.
I suspect this might be how I'm releasing my update:
1st time I made it automatically release when Apple approved it
2nd time I set a new release date for the next day, but when told that this would remove my app from the app store, I panicked and used the Release Now button for my app in ITC. I'll try and be more patient in future ;-)

How have you released your updates and did they show in the category by release date?