One band I was in had something similar, but it went a little bit further. We were an active band with a pretty full calendar. When our singer put in notice, his replacement came in rarin' to go and within a week of his audition he was sitting in with us for a good part of the set. He did the same the following week at what was supposed to be our previous singer's farewell gig. We had a week off the next week, so we had two weeks to get the new singer fully up to speed. So we scheduled a couple of full band rehearsals and some one on one rehearsals with our secondary singer/rhythm guitar player. He never showed up, called, texted, or emailed. So we ended up having to bring in someone else, our second choice from our singer auditions, and our former singer stuck around for another gig.
Month or so later, singer that disappeared left a note at our rehearsal place apologizing for bailing and claimed he couldn't contact us sooner because his house had burned down and he had lost his phone.