I never loan stuff because of reasons like this.

I'd never deal with drama like this unless it was my children - but as a parent, I'm actually parenting, so the odds of something like this are drastically lower.

In many states, for example I know in Texas, the seller can give notice to the DMV online of the sale. This doesn’t result in the new owner having taken steps to get the title, but does create a trail that the transfer actually occurred and gets the previous owner off the hook. May want to consider this option as well.

Daughter's bratty retort: "Fine, if you want it back badly enough, come get it."

Sounds to me like Daughter gave it back to Sis, though if title reassignment was completed by Sis listing Daughter as owner it's complicated, perhaps even if the title was never submitted to DMV. If Daughter decides to contest ownership, it becomes a legal matter, but doesn't sound much like Daughter is buttoned-up enough for that.