The stock's peak market cap was $62.3BB. Plus the bank was certainly trading at a premium to book value somewhere between 30-50% (1.3 to 1.5 price/book value is conservative for that era but I can't pull up any old balance sheets on yahoo finance to give a certain ratio)
So even if the price to book value is 1, I don't see how there can be an extra 90BB from what you've estimated (not to mention the billions of losses they posted in 2008)
It would make sense that it was in the high 30BB because a stock price of $44 x 900MM shares o/s is definitely not 60BB plus like what the other article stated.
Edit: interesting to note that the article highlights that in 2006, WaMu had a negative cash flow growth rate of 33% and states "The fundamentals are all spiraling downwards. Not the kind of trend a long term investor wants to see."