AMA did not always track numbers, and lost a bunch of records when they moved from Reston, VA to Muncie, IN. Unless you're a life member, your number doesn't always stay with you. If you drop out for a year or so, you'll likely be assigned a new number upon rejoining. I'd suggest contacting these folks in case your plane was a known competition model: http://www.control-line.org/DesktopDefault.aspx?tabid=1
Also look inside the cowl and fuselage to see if there's a name. You might get lucky.