[Jens Wendorff]

In aerospace, we use something called "anchor nut". Its a cage with a floating nut, available in most metric and imperial sizes. The cage is riveted by 2 small rivets to the body. This can be a good replacement if only the thread is worked out.
Another method is to use a special sort of blind rivet-basically a 'rivet-in-thread!.

But both methods require the flange still there, of course.

Jens