It would probably be safe enough to take the feeder away for an hour or so, maybe once or twice a day, to encourage them to eat the spilled feed.Our chicks are 2 weeks old. We have a chick feeder that they are constantly wasting a large portion of the food by dumping it on the ground. If I let the feeder go empty - will all of them find food from the pine bedding? Or is that too mean?
But I would not do much more than that.
Overall, it is probably better to consider that feed permanently lost, and try to come up with a way to reduce spilled feed in the future.
Are these chicks the only chickens you have? If you have older chickens, you could dump the chick bedding into the big chickens' run, and they will probably scratch through it and eat some of the chick feed.