I set up a sample survey for a new customer on a 4.0.3 installation yesterday, and found that the module simply disappears after the survey is answered.  Tried it again on a 4.0.2 installation in house, and found the same results.

Looking at the HTML, after a survey is initially answered, this is all that appears:

<div id="dnn_ctr463_Survey_pnlResults">
  

 </div>
<!-- End_Module_463 -->

The survey is marked public...  I haven't looked at the code yet, was curious if this was for some reason the intended behavior.  I would think that you would leave the survey results up so respondents could see the results change...

It happens when you never "Update" the module settings.  If you look at the defaults, it appears that everything is set correctly for a public survey, so I didn't hit update.  However if the settings aren't found, the results page defaults to private, and don't display.