The correct spelling of the phrase "wast alive" is "wert alive." The reason for this is because the phrase comes from an old form of English, specifically Middle English. In this form of English, the verb "to be" had different conjugations depending on the subject. For example, the present tense form for the second-person singular was "thou art," while the past tense form was "thou wert." Therefore, "wast alive" should be pronounced as /wɑːt əˈlaɪv/ and spelled as "wert alive."