Now I’m most likely not going to be hired and need to restart my job search and this will have derailed my entire plans for the first few months of this year. I won’t see a cent.
Next time when someone agrees to hire you in the hypothetical future, you will keep looking and interviewing, at least until you have accepted a formal offer from someone.
(I'm assuming here that they didn't give you an actual, formal offer even if they did tell you about a starting date)
I've turned down job offers in the future, because they're empty promises. You're a hiring req in some drawer, until the first day, because everyone is aware it's an empty promise.