Once a request is merged into another, it is gone. Would you consider having HS display something nicer like a note that says “this request was merged with request foo” with a link to request foo instead of “There is no request with that ID”?
Otherwise, if you have a link to a request that got merged, your link is useless and you may be perplexed, or quite possible even flummoxed.
P.S. I love the new option called “Return to the request after closing”.