Oh, my bad. I missed that you uninstalled it. Did you also remove the files from the add-on, and revert template edits you might have made for it?
Turn the listeners back on, by the way, as that basically disables a lot of functionality. It is mostly used to ensure you can access the Admin CP after a poorly coded add-on might prevent the forum from running properly.
The one thing left that I can think of is that the add-on used the same content-type as the XenForo content-type uses (conversation_message), and that uninstalling the add-on removed the xenforo data as well as the add-on data.