Many of the wikidata entries have diacritics in their name. Autocomplete during data entry requires the name be spelt with the diacritics to show up.
For instance, if you typed "San Nicolas", you would get several entries for the city in the Philippines. However, if you typed "San Nicolás", then you would get the city in Mexico. The Mexican city would not show up by typing "San Nicolas".
In common usage (especially in English), the diacritic may or may not be used, so it can sometime be difficult to match the correct target.
In this case, it seems like typing "San Nicolas" should show both the Philippines cities and the Mexican city (i.e. "San Nicolas" would match either "San Nicolas" or "San Nicolás").