Just an update, I GOT IT OUT! LOL
I spent an hour here and there, suck all the fluid out with a suction pump so I can see things better, still can't find the broken piece. When I was about to give up, I use a coat hanger and bend a little elbow at the end, took the broken piece out. Thanks god 1000 times. The broken piece probably sit there for a while, no grinding, the end broke flush so I don't worry.
FYI, even they call that a tranny pan in the parts microfiche, it is actually an engine oil pan, the tranny drain passes through the pan, anything drop in the tranny will not go to the bottom pan, it stays in the tranny housing. I was reading a lot of dipstick corrosion problems and fell in tranny, I am going to cut the rest of the dipstick and use it as a cap, keep a spare one just for checking tranny level.
Thanks everyone trying to help, I am a lucky one this time!