This appears to be a colloquial or dismissive reaction, possibly pulled from a social media comment section or a forum discussing the video or case mentioned above.
"MIA" and "19-year-old Face" most likely refer to , a 19-year-old college student who went missing (MIA) from her apartment in Orlando, Florida, in September 2021. Her disappearance led to a massive search effort involving the FBI and hundreds of volunteers. HD HIKR-119 My Ass- I See. MIA 19-year-old Face...
The video features an actress identified as MIA , who was 19 years old at the time of filming. This appears to be a colloquial or dismissive