Star jasmine (Trachelospermum jasminoides) is a tender evergreen vine, but does not do so well where the winter temperature drops. Its response to cold is to drop its leaves to cut down on water loss. I expect that it will start to leaf out shortly in response to the spring weather and you will have plenty of flowers later on. Don't expect it to hold its leaves all winter in zone 7a, unless you can protect it in some fashion. However it won't do it harm for it to drop its leaves annually.