Assuming for 3 days the bait bucket and minnows were not outside (otherwise they would be frozen) one has the distinct possibility of killing the minnows with thermal shock by replacing 50F-60F water with 34F water from the water in the ice hole.
The bait bucket is one of those thick styrofoam ones. It sits in the garage, outside on the step, or in the back of the pickup truck. The FH are always is 34ish degree water around here in the winter. When the bucket freezes in real cold weather the FH all move to the center and wait for a bucket warming trend.
