It could be that this port is open but is directed to a non valid ip.
This is from my experience with my router.
Eg. your ip is 10.0.0.3
and you have setup to forward port 1025 to ip 10.0.0.50 which is unused. This would explain why the port is open but appeaers stealth as it does not function.
Ps i may be up the wrong tree here!!