Assuming your council is not a planning authority but a consultee on local planning applications it is not unknown for an applicant to withdraw an application for planning consent. If that is the case you would be able to see on the online planning portal that this has happened in which case there would be no point in discussing it at a parish council meeting, even if the agenda had been issued with the application listed on it.
We do defer agenda items sometimes if the item lacks sufficient information to make a decision on but planning applications need to be responded to within a set timeframe so probably not appropriate for a planning matter.
The only other possible explanation is if declarations of interest on the application are made leaving too few members (i.e. below the quorum) to discuss the matter. That also happened in my council once when our planning committee meeting was barely quorate (a quorum of 3 and just 3 in attendance) but one councillor declared an interest as the application was his own property so withdrew but this left the meeting inquorate so the application couldn't be discussed. As individuals, of course, anyone can comment on a planning application online.