Why would you have to close a flight plan that has not been activated? If it is not activated a reasonable time after the stated departure time, it just falls out of the system.
OK, I was a bit slack there. Let's say I have successfully departed as per the VFR Flight Plan, thereby activating it. Here's the key question: if I then fail to show up at the destination, and have made no emergency calls etc en route -- I simply fail to show up within the planned window -- will the destination ATC (or the departure ATC) take any action ? are they obliged to take any action given that I have filed a plan ? or will I simply fall out of the system or -- not quite as bad -- be at the mercy of the decision of ATC on the day ? This is what I am trying to get at: will the VFR Flight Plan "system" trigger a SAR response if I fail to show up on an activated flight plan ? or, as previous responders suggest, will a SAR-response only be triggered if someone (informally) assigned by me as a "flight follower" (e.g., friend/relative/flying-club etc) complains that I am missing (and then the VFR Flight Plan may be retrieved from the system to help locate me)...
(By contrast, presumably a no-show on an IFR plan will trigger a SAR-response etc, even without a "flight follower" i.e., ATCO are obliged to actively respond...)