The correct spelling of the phrase "wast unbelievable" is actually "was unbelievable." The error can be attributed to a typographical mistake, possibly due to a slip of the finger while typing. The IPA phonetic transcription of "was" is /wʌz/, pronounced like "wuhz," while "wast" is an archaic form of "was" and is pronounced /wɑ:st/. It's important to pay close attention to spelling and proofreading to avoid mistakes in written communication.