Could sliding down a slide damage my camera?
ESD will create an arc when it finds "ground," which in this case could be the actual ground, and the path to ground being the slide and/or yourself.  At this point you probably had several thousand volts between yourself and ground.  Here, "ground" could also be found in the playset, maybe even the slide itself, depending on what it was made of.  Basically, if you shocked yourself, you just found ground. :)

Here, it sounds like your camera or phone were on your person and therefore were at the same voltage as you and not in the path to ground.  Therefore, no current passed through them and they were fine.  

If those devices changed position in the circuit and the ESD current passed THROUGH them to get to ground, then they might have been in trouble.  This would have happened it you had connected a wire to your camera, the other end of the wire was stuck in the playset, and then you touched the camera.  Then you would have presented the camera with a couple thousand volts across it, and inducing a current to flow as a result.

Generally it should survive such an ESD hit, though.  The high voltage and current as part of the ESD shock would pass through the metal case, if its case was metal, and the electronics inside would not have seen much disturbance itself.  Most devices have decent ESD protection, as it is a part of many product standards.