Oh crap is all I can say! I hate it when stuff like that happens! Sounds like you aren't sure you actually dropped it in there which is worse than knowing you did. I hate that man. If you are like me, it will bug you until you find it. I would try the magnet and maybe it didn't go in there and is on your skid plate or something. My luck the magnet would come off the coat hanger! This may be the stupidest and craziest idea you ever heard, but can you get a shop vac and try to put it up to the hole on the side where the oil goes in or seal the top off enough and try to suck it out? If there is no oil in it they are pretty air tight I have done that on other things to get stuff out. I have also used compressed air to move something over to where I could get to it before. Now you are probably thinking I am a nut! But that is the only other thing I can think of without dropping the transmission. I will quit talking now.