Oil in spark plug well and missing spark plug

My 2009 Honda Odyssey EXL has a slight tick for a while, but soon turned to a loud knock. I let it sit until I had time to work on it, but the wife ended up driving it and it died on her.

I pulled all the spark plugs, and on the #1, 2, and 3 cylinders there was oil in the spark plug wells. I pulled the plugs out of 1 and 2 and when I attempted to remove #3, it wasn’t there. There was nothing in the well. The strange thing is there was nothing to thread a plug into at the bottom of the well. Just a gaping hole as seen in the second picture. The first picture is of another plug well