Westjet - Bank Dollars Expiry

Hi, I re booked a flight today - August 15th, 2011 for a return trip from Halifax to Toronto. I thought I had the the $$ for the full amount but I found out that my earlier credit of $ 150.00 had expired about 12 hours before on August 14th.  I was told the money was gone, and could not be recovered. Am I disappointed - yes.  I did not receive any notice it was about to expire otherwise I would have re-booked on the 14th.   Disappointed Customer.