After checking the SmartSuite API documentation several times, as far as I can tell we can only search for a record using the record ID.
This is very limiting when connecting to other applications since potential new data from the external source will not have any SmartSuite record ID (that we know of at that time). We have no way of validating the existence of a user already in the database.
Please implement an API search option using another field other than the SmartSuite specific record ID such as name or email address (or any field would be best).