Creating objects or classes using the relation datatype does validate if node exists on public API, this will show the following error in debug

Error: eZContentObject::fetch 	Feb 13 2013 10:15:57
Object not found (999)

This happens when setting a default location in a class 'selectionRoot' or when you set a object relation field of an object to a non existing folder
Tested using tc-1231 and tc-1487
https://gist.github.com/jpingo/0edf2fc0a89274617e42