A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Solving The Riddle
Limited: Search your deck for a Ring card, reveal it, and put it in your hand. Before this turn ends, if the Ring you revealed is not in play, discard either that Ring or your entire hand.
I Play solving the riddle to search for a ring, and discard it during my turn. Before the turns end, The delayed effect happens: Can I choose to discard the Ring, which means I don't discard anything, as it is already in the disacrd pile?
I Play solving the riddle to search for a ring, and discard it during my turn. Before the turns end, The delayed effect happens: Can I choose to discard the Ring(?)
http://rules.l5r.com/Effects#Choices: "A choice may be made even if its consequences would be negated or otherwise fail due to lack of suitable things to affect.
"Example: If a Personality is already bowed, or can not bow due to an effect, you may still make a choice to bow him. If you do not control any unbowed Personalities, you may also make a choice to 'bow an unbowed Personality,' which just fails."