The point is, I will show you well endowed ladies one ingenious use for your 'dead' underwires; and I will show ALL of the rest of you one ingenious way to make sure you never need those discarded underwires!
One exposed underwire. (Cup size does not matter, the general "U Shape" of the underwire is what makes this work.)
An escaped drawstring
The garment from which the drawstring escaped
A Needle (OR)
A Sewing Machine
Scissors for trimming stray threads
Step 2: For the "Rethreading/Underwire" Portion
Thread the free end of the underwire through the open drawstring seam and pull it all the way through. That's it!
Step 3: Now, to Make Sure It Never Happens Again...
Step 4: Center the Drawstring.
Make sure that the drawstring is showing a roughly equal length on both sides. (This is relatively permanent unless you plan to employ a seam ripper, so make sure the drawstring is where you want it to be!)
Step 5: Sew by Hand (OR)
The point is to sew THROUGH the drawstring to anchor it into place in its pocket, so that it will no longer be able to escape.
Step 6: Sew With a Sewing Machine (Isn't Technology Amazing?)
If you have a sewing machine, I'm hoping that you understand how feed dogs work and what the reverse button does.
So, stitch the first seam over the loop/pocket with the drawstring in it, backtack BACK over the drawstring, release the reverse and you're done!
You've anchored the drawstring inside the pocket, it can no longer escape.
Step 7: Annnnnd, Done!
Questions? Ask away, I have a tendency to assume that I explain myself well, when that is not always the case!