一道非谓语动词的题目

题目

一道非谓语动词的题目
Did you find out who had stolen my watch?
That child didn't admit _____
doing that / having doing that
为什么选后面一个?

答案

admit doing sth.
“偷表”这个行为是作为过去完成的事,答案是否有误?
having done that——我认为答案是这样的