only if thread A doesn't unlock it before thread B issues the destroy. So if your code between lock and unlock is fast, and it should be, then you won't see this very often.
you could try grepping for mutex_destroy in your error log for kicks.
So, did you post this to the AOLserver list, or just send private email to Jim? Jim is not involved in the day to day development of AOLserver, and you might want a wider audience for your concerns. Discussions like this should be on a public list.