If you remove an application from sale, updating it does NOT automatically make it available again. You need to go to “manage your applications” in iTunes Connect, click on “Edit information”, go to the pricing tab, and select any stores you want to sell it in. After you save changes, it will show up as ‘ready for sale’ on your application page. You can also do this without updating the application or if it’s still in review. This is hidden in the FAQ.
I made both I Can Has Cheezburger (ad free) 1.5.2 and ICHC ad supported 1.5 (v1.5.2 is still in review) available a few hours ago. It still hasn’t appeared yet, but hopefully they should be available before too long.