The purpose of someone moving a motion (proposing) and then having a seconder of the motion, is to establish if there is any support for the proposal. If it's not seconded, the matter falls.
Parish Councils don't always formalise their resolutions by voting, even if that's what it states in the Standing Orders. Sometimes decisions are reached by consensus, and the decision will be clear to the Clerk (hopefully). When the minutes are submited to the next meeting, if Members accept those minutes as a correct record, then, as Answer 1 states, it would be difficult to challenge.
I have had personal experience of this where a Parish Council (months after the event) was convinced it had made a certain decision, le's say X; I pointed out that the decision they had taken was Y and was able to refer to the minutes. They had to accept that the decision Y stood and I reminded Members that approvng minutes of meetings was an important part of their role.