Nesting duck with eggs

I live in a roof top apartment in south Buckinghamshire and have a large veg box which by accident when I start to clear it of some old plants and weeds a duck jumped out and flew off. I was carful not to touch the nest directly but discovered 3 eggs left behind. I left the nest and area alone and went out, that was about 4hours ago and it doesn’t look like she has return yet. 

Would she come back?

How long should I wait before doing anything?

Who should I call?

What should I do and how quickly (it’s a Sunday so not many places open)?

I’m have a roof top apartment so I’m not sure what would happen when the ducks would do once hatched anyway.

thanks for any help