Until we netted our ponds we lost our koi and goldfish to water snakes, kingfishers, herons, snapping turtles and huge bullfrogs.

A raccoon would make a mess out of the pond if it was the culprit, they tear up plants and your pond looks like a tornado hit. They often leave scales and fins and bones too.

Herons and Kingfishers leave no trace. The fish are just gone.

After the power went out yesterday for a few hours, the waters will still from no pump or fountain working and Lo' and behold, out comes the alleged missing Koi from under the fountain. The odd thing is, he used to swim around freely eating. Dont know why I couldn't see him all of a sudden. Anyway, I'm glad he came out of hiding.

Your story is similar to mine Pete... About a month ago i bought two new small koi (5-6") On my way home from the store, one started acting funny, then once i released him into the pond he went into shock... I called up the guy i bought him from and he said to just leave him, he'll be fine. The next morning i went out to the pond to see how he was and POOF he was gone. I did like you, checked under the pumps, in between every single rock and crack, checked the entire surroundings of my pond- NOTHING. he just completely vanished... do this day i do not know what happened to him. Fortunatly though my supplier replaced him for free :)