You are right, it is a problematic question and hard to give an aswer.  It would depend if the child was born in China or not.  Local Courts will be more inclined to intervene if the child was born in China than abroad.

Also, the Chinese side of the marriage in question could just ignore the divorce decree issued abroad, and file for a local divorce.  In Chinese Family Courts, both husband and wife must be present in order to proceed with a divorce decree.  But if the Chinese side has enough "guangxi" and money, they could claim abandoment and not knowing where the foreigner is, and get what they want.  Of course, such Court decision would be honored and good only within China, a [previous Court order will have precedence over it, but only outside China.

And for your information, China is has not signed the Hague Convention agreement of kidnapped children, so that approach does not work here either.

No, China is not a state signatory of the Hague Convention on the Civil Aspects of International Child Abudction. 

If you took a survey on this the majority of the people would say they would not recognize the child custody decisions settled in another country. It just like like anything else if you don't have access to read it anywhere you won't know.