So even though I started the thread, I forgot to use my mystery reward certificate before it expired on Sunday.
I called the automated BB help line and it asked me for the phone number associated with the account. Once I put in the number it said - you have recently expired certificates, would you like them reinstated. When I answered yes, it reinstated this certificate along with another that recently expired and gave each of them an additional 60 days.
Not bad considering the original mystery certificate had a 10 day window!