i think i lost a cog

[axhed]

okay so, i unlocked the door to the machine room, and off in a side room i found a big cog that just seemed to be a fluff enviromental piece, so i threw it into the corner of the room in a pile of boxes.

got to the bottom, found the machine, put the two closest cogs onto the machine there, and went back up in search of the third cog. i found it in the pile where i threw it (in the room with the machine that takes the rods i believe) and picked it up. when i spun out of the corner, it caught on the vertical pipe there in the corner and disappeared from my hands, never to be found again.

since then, i found all the rods and inserted them correctly, balanced the pressure, put coal in the oven, and reloaded the game twice, but the machine won't start; says it needs more work. sooo,

is the third cog needed?

where did it go? do i have to restart the game?