They are wild but they were found in the middle of a lake with speed boats racing by. We left them for a little while but no mum duck was around. I have raised chicks before but we got rid of our brooder and our heat lamp so for now what food and heat would work. They are in a shoebox with hay.
Just curious, but, how
long did you wait?
Speed boats could have scared the mother duck - it's not like she's a mammal and needs to "feed" her babies - so she could have been hiding until she felt it was safe to return to her babies.
If you say they have "just hatched" then mother duck will not be far away; after all, she had to incubate those eggs up until hatch time.
I'd be inclined to take them back and wait it out for mother duck to return; but, I understand that you may not wish to do that.
Heat can be provided by an anglepoise lamp. Food should really be specific for ducks, but, if you have none, some finely chopped boiled egg yolks would be ok and maybe some mashed peas until you can get the right food.
You will need to rethink that shoebox extremely rapidly because they will double their size almost daily!! Ducklings are reknown for their speed of growth.
Water is very important: I used a small plastic bottle, with a square cut out of it for access, so they could dip their whole heads in to clean their nostrils and drink. But, it will get messy, very, very quickly!
Good luck, whatever you decide to do with the ducklings be it 'return', rehab, or rear