We recently had a lone chick. It was the only one that hatched under my broody hen, ( the rest were unfertile) we removed him from her when she stood on the partly hatched chick crushing him and all the shell around it. I was worried it would die, so I popped it in our incubator to hatch in peace.
Two days later when it was all fluffed up and eatings and drinking, I popped it back under my broody just before bedtime and they are now happily scratching around in the run now.
Glad I returned the chick really as it has now snapped my hen out of her broodiness and hopefully after raising this chick we might get some eggs from her again.
If you would rather keep the chick and raise it yourself then I have used a small stuffed teddy in with a lonely chick and it gives it something to snuggle up to and stops it cheeping so loudly.
Otherwise you could use it as a very good excuse to buy some more
Steph xx