The correct spelling of the phrase "wast session" is actually "was session." The pronunciation of the word "was" is /wʌz/ which is spelled with a "s" rather than a "t." The word "session" is pronounced /ˈsɛʃən/ and is spelled with two "s's." The phrase "was session" refers to a session that has already taken place, whereas "wast session" is simply a misspelling. It's important to pay attention to spelling and pronunciation to effectively communicate in spoken and written language.