It's a crime to make a false report of an abduction.

However, I believe this phrase covers your basses.

"I believe a minor is with someone other than their PARENT being taken across the state line."

As long as all of those points are factual, that should be a good reporting.

If they ask where...

That's up to you, because unless you were at the state border and witnessed it, you'll probably be lying.

You can always say,

I know this information is taken down, and too many people are being doxxed nowadays, so I don't feel comfortable saying where, because if this is a smuggling operation, they can FOIA public cameras and find me.

A stretch... but none of that is incorrect or untrue. Just might have some temporal holes.

Via con dios.