I am not aware of such a bonus. There are, at times, boni for signing up to the RBC WestJet Mastercards which earn you WestJet Dollars as a percentage of your spend with that card. Maybe you remember that?
"To qualify for this bonus offer, you must enrol in WestJet Rewards and book a minimum of one WestJet flight between February 15 and March 31, 2013 for travel by June 26, 2013. The following blackout dates apply: March 28 to April 2, 2013 and May 16 to May 21, 2013. New bookings only. Enrolment in WestJet Rewards prior to flight date is required and your 9-digit WestJet ID must be included on the booking. Bonus will be awarded after travel is completed. This offer is valid with the purchase of any published fare of a regularly scheduled flight marketed by WestJet. WestJet Vacations bookings and partner marketed flights are not eligible for this offer. Please allow up to 30 days after travel is completed for the bonus to be processed to your account. Limit of one bonus per member; cannot be combined with any other offer. Offer valid for new WestJet Rewards members only; not valid for members enrolled prior to February 15, 2013. Bonus WestJet dollars have no cash value and are subject to current program terms and conditions. For more information on WestJet Rewards, visit westjet.com/rewards. Offer is subject to change without notice."