Under CA law we can not compel identification from people who are merely detained. Hiibel was in NV where they had such a law that required identification.
Here is how it pertains to CA as advised to law enforcement by the Attorney general:
The U.S. Supreme Court has drawn a distinction between a detainee's duty to identify himself and his duty to answer non- identification questions during a lawful detention. In Berkemer (1984) 468 U.S. 420, 439, the court stated that a detainee is not obligated to answer any questions you put to him during a lawful detention. (Christian (9th Cir. 2004) 356 F.3d 1103.) However, in Hiibel, the Supreme Court clarified that it was not referring in Berkemer to questions regarding identity. The court upheld as constitutional a Nevada "stop and identify" statute and found that a detainee's failure to identify himself could be the basis for a lawful arrest under a companion statute almost identical to Penal Code section 148. (Hiibel (2004) 124 S.Ct. 2451.)
Unlike Nevada and 20 other states, California does not have a statute mandating that a detainee identify himself, and that obligation cannot be read into Penal Code section 148. Although you may take whatever steps are reasonably necessary under the circumstances to ascertain the identity of a person you have lawfully detained, Hiibel does not provide a means for arresting someone for failing or refusing to identify himself. The Ninth Circuit has ruled that a suspect's failure to identify himself cannot, on its own, justify an arrest: "the use of Section 148 to arrest a person for refusing to identify herself during a lawful Terry stop violates the Fourth Amendment's proscription against unreasonable searches and seizures." (Martinelli (9th Cir. 1987) 820 F.2d 1491, 1494; Christian (9th Cir. 2004) 356 F.3d 1103, 1106; see also Quiroga (1993) 16 Cal.App.4th 961, 969, fn. 2.)
In your case, the officer may have demanded it but unless he had something more, he could not have arrested or charged your fiance for his failure to provide any DI.
At this point, he can make a personnel complaint against the officer but that's about it.