Bus 81 is rarely full so you could use that to get back. If you do want to walk there is a sidewalk beside the main road all the way from Villefranche to Nice. It is about five miles to Place Massena but it is a much nicer and shorter walk, with spectacular views, if you go through the Parc du Mont Boron. For this you set off on the main road and a little beyond bus stop St Esteve you will see some steps going up the hillside. Climb these and continue to climb when you arrive at a rough path which leads up to a surfaced road. Turn right here and continue to climb past houses with wonderful views of the bay and some expensive new villas. At the highest point on this road you will see a drinking fountain to your right. A little beyond this you will see a surfaced path heading down hill. The path will take you to Boulevard du Mont Boron where you can cross and drop down again to the coast road a mile or so from the centre of Nice. This route reduces the walk by at least a mile but adds a considerable hill. The shortest route is to climb from Villefranche up to the Col de Villefranche and down the other side to Riquier, cutting another mile off but it is not nearly so pleasant as the Mont Boron route.
A final alternative to all of the above is to catch bus 82 which leaves from close to the Welcome and, going round many sharp bends, follows the Col route to Riquier station, which is about a 30 minute walk from Place Massena. It is a small bus but I have never seen it full. There are, by the way, plenty of restaurants in Villefranche that will be open at 5.00pm. Some never close between 9.00am and midnight.