Well, if it was hooked up to an Onkyo amp, all it is doing is sending low energy signals, which originate in an Onkyo remote, and are sent to and from the dock from the receiver. Since you don't have an Onkyo remote (and an HK receiver wouldn't know what to do with those commands anyway), I seriously doubt anything was sent to or from the dock over the RI cable to begin with.
And even if something did go through, it would probably be ignored by both units. It's not like a fully amped electric charge like what is sent to the speakers would ever be sent through.
Don't believe everything on the Interwebz! A duck's quack DOES echo!