First, are you absolutely sure that the female is the swan that is missing? We ask this question because it is usually the female that cares for the cygnets. The male may leave the immediate area to patrol the perimeter of the habitat as we have seen this in several swan pairs. The male will still remain within earshot of the family to return and protect them if necessary. But, 2 weeks is usually a very long time to be separated.
We have also heard about male swans that will find another mate and have 2 families. So, without being sure that it is the female that is missing, it is difficult to know if either of these scenarios fit your situation.
Finally, regardless of gender, there is always the possibility that something happened to the other swan. If attacked by a predator, serious injury or death could be the reason for the separation. If killed by a hunter, state or federal wildlife official (yes, there is a concerted effort to kill Mute Swans so the habitat can be freed for the introduction of the larger Trumpeter Swans for Trophy Waterfowl hunting), then obviously the swan will not return. If the other swan were to be ill, it would go away so as not to spread disease to the family. If it recovers, it will return.
Again, a 2 week separation from the family is highly unusual, but we have heard of extreme separation for whatever reason, only to have the missing member return. Please let us know how this situation progresses and if the swan parent returns. The Regal Swan