Interesting ... I also have the post office coming attractions emails and they had my ballot coming but it didn't show up until the day before the election 3 weeks later so they do make mistakes at the local office level.
They have to put a trace on it.
How to put a trace on a missing 1st or 2nd Stimulus payment. IRS for Payment Issued but Lost, Stolen, Destroyed or Not Received
See question F3 here, you can expand it to see how to put a trace on it.
https://www.irs.gov/newsroom/2020-recovery-rebate-credit-topic-f-finding-the-first-and-second-econom...
