If it died you'll likely never find it, as someone else said, if you have a sufficient cleanup crew its body was disposed of by the cleanup critters and you won't have to worry about much of a cycle issue. Sucks to have to wonder about it though. My Yellow Coris Wrasse hid under the sand for 2 weeks straight before I found it and had to scoop it out of the sand with a net.
It is important to not buy creatures that are doomed in captivity, because as said, it does promote the collection and selling of them. To "rescue" creatures from the LFS also sends the wrong message. If it sells, they will get more to sell, and it doesn't do the species any good. Not flaming on anyone, just saying, it is a money driven industry, and if it makes money, it will be collected and sold, regardless of its disposition. We must take into consideration the effects of our hobby on the natural reefs and the fish that dwell among them and do the responsible thing. This world only has so many resources and humans tend to use them up selfishly and greedily.
Bengaii Cardinals, nearing extinction, but you can bet you'll keep seeing wild-caught ones in stores because people are uninformed and buy them, and the collectors know they sell like McDonalds cheeseburgers, so they could care less if they go extinct, they're going to make every dollar they can off of them until then.
I'm not saying Cleaner Wrasses are nearing extinction, or even endangered, but they have no place in the aquatic hobby. Nothing that can't survive long-term in captivity has a place in this hobby.
Neon Goby's do a great job of cleaning fish, and they will live off of more convenient food sources when all the parasites are eliminated, plus, their color is very similar to a Cleaner Wrasse.
Please don't take anything I said as flaming. I just want to shed some light and help save the world, one fish at a time