There Seems to be a error in search in certain circumstances
I found a circumstance where searching for a chr record that exists in an index of Birmingham, england in 1808 does not get found when searching using the child's name. It does not find the record. But it finds the record only if searching using either parents names.
The record is in film 919767, index 7760346.
The chr record is for Eliza Sunderland, 1 aug 1808, parents john Sunderland and Mary.
This potentially is a serious flaw in the search engine, or there is a problem with this index.
This is a result of how the FamilySearch search engine works. During the indexing, the project instructions appear to have been followed to the letter, in that as the entry probably read, "Eliza, daughter of John and Mary Sunderland", the indexer has not recorded the first name against the child, but just against the parents. The screenshot illustrates this.
I have previously criticised this literal indexing of exactly what is written, as it often leads to children being missed in a search. If, a year later, another child has been recorded (in the original register) as, say, "Mary Sunderland, daughter of John and Mary", you will find this in the "results" list, as expected.
As an index is supposed to be a finding aid, I believe this way of indexing, whilst "technically correct" is most unhelpful. It means one has to undertake at least two searches to discover all possible children - one using the last name against the child, the other against the parents (usually the father, unless illegitimate). I don't know if other websites adopt this method of indexing, but I have not noticed a problem as I do in FamilySearch.
Incidentally, there is an additional problem with this record. During indexing, I believe there is no difference in whether the event is defined as a baptism or a christening, but during the process of getting these records online, if they are categorised as a "Baptism" they will be carried across as a Custom Event when added to the relevant individual, but if as a "Christening" this data will transfer directly to the Vitals section. The same event (if indexed twice) is often categorised as a Baptism in one instance, but a Christening in the other. This bad practice has been pointed out many times, but FamilySearch does not appear to recognise the need for any consistency in dealing with the matter.0
I have just discovered that at least there has been consistency, using your example, in how the records of the children of John & Mary Sunderland have been both indexed (children without last name) and categorised - Baptisms, not Christenings:0
Paul is correct. These records have been indexed without a surname for the child. FamilySearch indexes data as it shows on the original document and according to what the record custodian requested of us. If the document does not explicitly state a surname for the child, none can be indexed.
I understand how frustrating it can be to not have the search for a full name bring up a particular record. I regularly do a surname search that includes the parent's names to see if a child shows up that has not been found in other searches. This article offers more researching tips. Search tips for historical records0