That was my experience in Fairfax County, VA as Chief Election Officer for a precinct. Upon opening the polls, we validated and recorded the metal numbered seals as well as verified that the machines read 0 and the protected counters showed what our documentation said they should.
Closing the polls was very similar. We tabulated the results, including write-ins, and sealed up all machines, recording the numbers of the security bands used.
The final results were written out and posted on the door of the polling place when the facility was closed. The tapes, provisional ballots, and memory cartridges were returned to the County election office that evening.
It’s not difficult to have safeguards against shenanigans, but good processes which are time-tested need to be put in place and you need people who are dedicated to tight security.
A missing precinct, if procedures such as ours as described are followed, is simply not possible. Certainly not for more than a couple of hours or so.