Is there a jQuery UI "anti-sortable" that will let LI's be taken and from a UL, but always specifying order?

I have something partially working where there are two UL's, both having had jQuery UI .sortable() called on it. I am looking to have the second list really be sortable, but the first list retain a single ordering instead of having a LI from the second list appended at the end if the user clicks on it.

I see one painfully obvious way to do it: keep a JavaScript list of values of LI's, or alternately set a data-index='0' (then, 1, 2, 3, etc.), and then in either case make a single, possibly bottom-up, sweep of the dread bubble sort.

This appears to me something I could straightforwardly get working, but it has an "If you're doing it this way, you're working too low-level" code smell to me. Apart from a bubble sort reference, in a case where I think O(n) really is tolerable, it seems like something where someone who knew jQuery UI could produce a much shorter and clearer implementation.

I've outlined above the hard way of addressing my problem. What easy ways should I consider instead.