2003 mercury sable transmission trouble

[73demo]

i have a 2003 mercury sable went out and put it in gear it did not move l looked under it and all the tranny fluid was on the garage floor it has never leaked a drop before and i have drove it a few days and not a drop on the ground does this car have a vent tube or some thing that would cause this thing to blow all the tranny fluid out any help would be great thanks dale