This was, ostensibly, a normal day. Normal breakfast, normal drop off, normal walk, normal work call, normal dog. But she's disappeared so at least one unlikely thing has happened, quite possibly several unlikely things, because, well, here we all are.
However, unlikely things happen all the time. Strings of unlikely things happen all the time. They just don't have the eyes of the world on them, holding a microscope up to them, proclaiming how unlikely every scenario or combinations of scenarios are. Like coincidences, looked at individually they seem incredible, but it would actually be more unlikely that no coincidence, or strings of coincidences ever happened. Like the swiss cheese model of accident causation.