From this wikia:
When Rose prevents a police officer from checking Chris' ID, she seems to be defending him from a racist policeman, when in actuality, she doesn't want any record of Chris' location, in case law enforcement attempts to look for him when he goes missing.
This means she is very careful while hunting (she probably uses fake names, hunt people far away from her hometown, ...).
Also, the movie deals with the topic of racism and that black people's lives aren't as important as whites' are. From wikipedia:
The film also depicts the lack of attention on missing black Americans compared to missing white females. Slate's Damon Young stated the film's premise was "depressingly plausible ... Although black people only comprise 13 percent of America's population, they are 34 percent of America's missing, a reality that exists as the result of a mélange of racial and socioeconomic factors rendering black lives demonstratively less valuable than the lives [of] our white counterparts."full Slate article
This is humorously shown in the film: When Rod Williams recognizes Logan as missing (for several months) person Andre Hayworth, suspecting a conspiracy, Rod goes to the police but is derided (i.e. the police didn't care at all).