You're partially right -- the dynamically added controls don't exist anymore after the postback. They won't get re-added until the DataBound event is run. The problem is that Databinding events happen after control events, that is, after your button's Click event. So, at the point in the page lifecycle where the click event is handled, those controls haven't been recreated yet.
Here's a related question which might have some useful informationHere's a related question which might have some useful information.