Morning Lorraine - with computer databases, you can only find what is there - not what should be there !
When the handwriting on a census return is not very clear - someone trying to type the information into a database can often get it wrong. In the case of Frederick, his surname has been typed in as "Lam" on one site and as "San" on the official 1911census database and another popular site.
If you look for Edward Church in Warwick- you will find Frederick at the same address.
Sorry for not making things clearer - Derek