I've looked for a trap and can not find one. All I can see is the circular ring of square holes in the bottom. There are some small clumps of stuff in these and I've picked out most of it.

But to complicate things someone who was trying to help unscrewed a circular plastic plug from the side of the Dishwasher. It's about the size of a Nickel and has prongs in it that match up to a corresponding plastic nut on the inside. However this is free floating and I can's seem to get the plug back in. What is this thing? What are the dangers of running my dishwasher without it. It has holes in it so some water was going in it already.

1) Is there a screen or trap in the dishwasher that I can clean? I've looked and can't find it.

2) How can I get this little plug back into my dishwasher?