In your case there is 3 options
1-Even if you destroy the toolbar (button x) can close the form from the defined window but must be as this code ( add a close statement):

DEFINE WINDOW RepWindow ;
   FROM 1, 1 TO 20, 20 ;
   TITLE "Report Title"   close   

2-to hide the x button toolbar, can dock the toolbar for ex at top.then when you issue the close option in toolbar, the report closes

3-can try with listener object option, even if you lost the toolbar, you can restore it with rightclick on report.

of course issuing ESC closes the report.

update : can also add the statement "system" to see the close button (as windows system) on defined window

DEFINE WINDOW RepWindow ;
   FROM 1, 1 TO 20, 20 ;
   TITLE "Report Title"   system   &&close   

*second update
this follow code preview any report (print) using listener vfp9 class.the toolbar is docked and even if you free it and close it ,can rightclick on report to restore it--see the attached.

oListener =Newobject("ReportListener")
oListener.ListenerType=1
Report Form ? Preview Object oListener