Misconnected interconnect

I took my system apart the other day, and in putting it together I temporarily attached one interconnect from the cd player to the single-ended OUTPUT of the preamp, rather than to the single-ended INPUT.

Fortunately, I discovered the error before I played any music.

The preamp and cd player were both powered at the time (ie, both were "on," but not otherwise in use).

My question is whether what I did could have damaged any of the circuits. Ie, despite not having played any music, is it possible that a brief mis-connection in this way caused damage to any of the circuits. (Assume "standard" forms of wiring, if there is such a thing.)
i bet i sold several hundred tape decks in the 70s whose owners took them home and hooked them up backwards. no damage then. i,m sure it is playing now?
Probably and hopefully not. But it's a good idea to unplug everything, before changing interconnects, and speaker wire too. Some equipment has some voltage build-up on the chassis and the RCA outer shield ring, when it's plugged in and even turned off at times. I've seen them build up to over 50 volts at times. If you bump the RCA's center connector pin to this first, it can easily do damage.
The preamp and cd player were both powered at the time (ie, both were "on," but not otherwise in use).
this has always been a BAD idea & always WILL be! Switch off all your electronics & change the cabling - don't try to take a short-cut - you will eventually pay the price & end up spending a lot money repairing the unit due to sheer negligence...
If your equipment runs fine (which I'm thinking it should) take this as a warning from your equipment & never repeat...
XLR is superior in that respect since it cannot get loose, be plugged into output instead of input and cannot be touched since exposed inputs are female with recessed pins.

Plugging and unplugging should be done always with everything switched off even if it doesn't make a difference - just to set good habits.
I have hooked a preamp up backwards before (amp to inputs and source to output). There was no long (or short) term damage done. The funny thing is, it still played (a little)- You wouldn't think there would be any sound at all?