The other night I unknowingly plugged a component into the OUT rca's of my ref4

. This of course was aided by the lack of labeling. The crazy thing is -- everything sounded 'fine'. Nothing that I heard suggested I did something wrong. Only after I looked at the back of my Ref 4 did I discover my error, so i quickly unplugged the component.
I'm wondering if plugging into the out RCA's could have damaged the unit in any way. Any thoughts? The good news is nothing sounds obviously wrong, but I think I may hear a difference in certain things -- less shimmer and punch -- but I'm hoping it's just my mind playing tricks on me now that I know what I did. I'm not electrically knowledgeable, so I'm hoping the group here can give me a definitive answer (and preferably tell me that nothing could have happened and that everything is fine.)

thanks