[Greg Jones]

If you go to 'Preferences>Data', I'm guessing that you have 'Clean Up Inbox items which have' set to 'A Context' or "Either a Project or a Context' and 'Default List for Single Actions' set to your Ideas project. Change the preference to 'Both a Project and a Context' and the task will stay put until you assign both. You can also change the preference for the Single Action list to a more appropriate folder.