Ricordea killer?

[Lance]

What in hell is eating my ricordea? 4 rics, each the size of a toonie have disappeared in as many nights. I haven't added new livestock to the tank in months. Set a trap for the last two nights, and nothing in it except nassarius snails. Anybody have any suggestions to the culprit? Tank is one year old and occupants are:

SF tang
foxface
coral beauty
2 occelaris clowns
ruby-headed wrasse
mandarin dragonet
yellow watchman goby
blue gudgeon
pajama cardinal
scarlet skunk cleaner shrimp
2x hermits
12x astraea snails
4x mid-size turbos
10x nassarius snails
3x feather dusters

The only posible fish culprits could be the coral beauty and fox face, but I have had both for many months and never noticed them show any interest in the rics. All the fish are well fed and fat. The 2 hermits have also been in the tank for a long time. I'm thinking maybe a larger crab that has grown unnoticed in the tank.
Any suggestions?