Thanks for letting me know. If SecurityAssist (and Dynamic Suite overall) can't handle additional fields in the query used for a "Forgot Password" page then I'll need to create a "Forgot Password" page from scratch.
For this website, each registered member is indeed assigned a unique member ID that is used for login - but if they've forgotten the password then they've probably forgotten the numeric ID so it's not much help on the "Forgot Password" page. I'm working with an existing membership with hundreds of registered members so I can't reasonably ask my client to change their existing set-up.
Thank you for the info.