Sounds like they went through the process I would expect. I am not overwhelmingly surprised that there was no response from other staff (with no knowledge) at 0030-0100. The exception would be the staff member who locked up but any number of reasons why they might not reply (driving, finished shift so no-longer answering, phone switched off, or actively avoiding call[!]).
The consensus of opinion from the 5 people locked in that it would it was the last one ..