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.
When I first worked there, we used the Shouptronic 1242 voting machines. They had quite a few areas which could be protected by numbered metal security bands and tags.
The new voting machines they switched to about 15 years ago were the touch screen enabled models running Windows XP embedded. They used Wi-Fi to communicate with one machine designated as a master to verify 0 prior to polls opening and synchronize vote totals after the polls closed. My gut feeling was there were some security issues with them but this was when the electronic machines were first appearing in voting places.
The Shouptronics printed out paper tapes from all machines and one machine was used to totalize all votes and print out a totalized tape. All paper records were affixed to the official forms and signed. The electronic machines just "phoned home" to transmit their results.
Of course even the old mechanical machines were able to be set to generate fraudulent totals. I read many years ago of a NJ precinct where the machines were tampered with to file down the teeth used for advancing the counter so that the Democrat advanced on every vote while any challenger had fewer counted votes compared to those actually cast.