Hi and a warm welcome to Rootschat
The purpose of censuses was that everyone should be recorded, so in theory that is the case, whether the person was at home, in hospital, in prison or in an orphanage.
1911 look ups rent allowed, so we cant ask for the name or help in that way.
But, yes, the orphanage should be there.
And you should be able to find your person with their name and year of birth etc as per normal.
Remember the person filling in the form at the orphanage may be unclear as to the facts.
The child may have a description such as "inmate" or suchlike