If you can put the rock back without crushing them that would be best. (it drive me nuts when people lift a rock and put it back down without thinking.) But really ants are good at moving house. They will simply move under a new rock, or under the same rock if it is in a new location.
So, don't worry too much. They are adapted to living in a world that can change suddenly in titanic ways. And their haste and panic are how they survive.