Awwww, that sucks. Hate to hear stories about stolen bikes.
I may have an older GF medium HT frame out in my shed, I'll check. How tall is your son? Does he def. need a small frame? Is he looking for 24, 26, or 29 inch hoops?
I'm sure the folks on the Nemba forum will step up and help get your son rolling again. I'm sure I have some bits in the parts bin that need a good home. Let us know.