Hey guys and gals thanks in advance for any info.

During this past winter we had a major leak in our bathroom that bled into the kitchen. Long story short the leak has now disappeared.

The leak started the day after it seemed our main drain seemed to freeze up. We ran an electric heater and it started draining again.

Any water used in the bathroom dumped directly out into the kitchen cieling (directly below the bathroom). We had to shut off the water at the street due to washed out valve stops. We have since had a plumber visit to replace main shut off valve and pressure regulator, and now have the water back on.

Now for the mystery.... There is no more leak. No matter what we run or how hard, nothing not a drip. The plumber could not find a leak either. I'm stuck, and dont want to replace the cieling/floor until this is resolved.

Again thank you for any ideas or insight

By your description, it sounds like there are at least 3 problems that need to be addressed.
1. Insufficient insulation on the exterior walls. The heat that should keep the pipes from freezing is leaking out.
2. If the problem just went away with heat, it stands to reason that the main drain froze. This isn't easy to accomplish even in very cold temperatures unless there is a blockage that holds the water in place, or the line is running uphill somewhere. As you didn't need to snake the drain, it indicates that there is a problem with the pitch of the pipe.
3. The leak itself. My first guess would be under the toilet. If it was cold enough to freeze the drain, it probably froze the wax ring and caused a separation that allowed water to escape. The reason may be something else, but that is the spot that I would check first. It would have been a good idea to open the ceiling at the time to both spot the leak, and allow the area to dry; but that horse has left the barn.

You may not be able to easily fix the slope on the drains if that is an issue (it may have been a blockage that froze), but the insulation problem needs addressed no matter what. If you haven't opened the ceiling, I would look for the evidence of the leak there first. If it isn't a bad wax ring, that may be the only way you can find the leak. I sincerely hope that you don't have lead drain lines that cracked.