To find ressie's online, find out the main phone number your reservation is under. For example, when I made my hotel reservation, the CM made the ressie under my profile that was already in Disney's system. The main phone number is my home number so any ressie I called in for used the home phone number by default as the reservation phone number - - unless I give the CM a different number to specifically override. When I make a ressie online, I use my hotel ressie and override with my cell phone number since it would be easier to get me at WDW with that number. Clear as mud??????
If you don't know which phone number the ressie is under, you can call and ask a dining CM, look up your WDW user profile online, or look up dining reservations online and try using different phone numbers you have - - home, work, cell etc.