Glad this is being looked into in an official capacity. Prayers for answers!
I'm sure this has been looked at over the years, but the "couple in car" MO stands out. Perhaps there are other (than what's listed here) cases related. Or, failed attempts at abductions?
Not sure what information you can reveal, or not...
Did the 4 door sedan have vinyl seats in the back?
Not saying this is related in any way to Anna, but within my family I'm aware of a child abduction attempt in the fall of 1978 in Washington state, about 200 miles from Seattle by a male and a female couple in a large sedan with vinyl seats in the back. The couple had brown hair. They attempted establish a rapport and lure the child into the back seat. The 1970's were a different time, and nothing was reported or done since the child hurried away. The couple in the car were never seen again.
All my own opinion, but the new information in Anna's case indicates there could be related cases to hers? Perhaps, some those cases could be re-looked into?