Why am I not given to option to search one of my Feature layers by the OBJECT ID? Im in Web map settings and not given the dropdown option

[AmandaWorzella]

I am using AGOL and trying to add a search by OBJECT ID field on one of my layers. It is not populating in my dropdown options for the fields for that layer. Do I not have the option to search by this identifier? I has a lock symbol next to it on the fields list, does that have anything to do with it? See picture below. 

[RussRoberts]

Feature search is based on string and integer fields and currently not on OID based fields or fields using subtypes or domains. https://doc.arcgis.com/en/arcgis-online/create-maps/configure-feature-search.htm