I sent an error report to Apple from my Mac about an issue with unexpected restart . Where will I receive the correspondence

It has been my experience that such reports are just for developers in the background.

If you really want some correspondence, you may just hear something is a duplicate bug, but a free login to http://developer.apple.com/ and a submission to http://bugreporter.apple.com/ should at least eventually give you an idea if it is being researched. You can't state the results of your report on this community.