How can I find a deregistered airplane?
Sorry to be the bearer of bad news. But, you have already asked this question on www.airport-data.com. A quick search in the FAA search database with the tail number or serial number (which can be found using the tail number) shows that it has not legally flown in the US in almost a decade. So, it is either sitting somewhere as a ramp queen, registered overseas, or not in existence any longer.
Try contacting the last person to register it. Otherwise, it would be like trying to find a salvaged car after it has been junked. It will only pop up if it is reregistered. However, you can pay a private firm like a law firm to research the aircraft’s certificate of title (or simply title). It would be like searching a deed.