What was Luna going to say?

[sylviablundell2001]

No: HPFGUIDX 82582

Forgive me if this has been mentioned before, but I was wondering if 
we missed something important due to Hermione's uncharacteristic 
arrogance.  Referring to the locked door in the Department of 
Mysteries, Luna says "You know what could be in there?" Hermione 
brushes this aside with the sotto voce comment to Neville "Something 
blibbering, no doubt" and we never get to hear what Luna thought 
could be behind the door.  Later, things start happening so fast that 
no one ever gets to ask what she meant, supposing anyone was 
interested.  I can't help feeling that they might have missed the 
chance of finding out something important.
Sylvia (who really likes Luna and hopes she will be the one to put 
Harry together again)