Damaged seedling re rooted - now what?

[Blue Star]

A squirrel chomped half a dozen of my Japanese Maple seedlings in July. In a panic, I put them in a clear shoebox sized tote I was using to grow moss (sphagnum and harvested from a rock).

I had 0 expectations of success, and to my surprise one vigorously rooted! The roots are sandwiched between the sphagnum and bottom, as well as in the moss itself. Roots are about 6" long now.

Should I just leave it in there until next spring, try to pot it up, or...? My biggest worry is frost damage with the roots touching the container bottom.

The evergreen spindle cuttings in the box also all rooted in 4 weeks, I'm starting to think this is a better set up than my cuttings prop box.

 

[Shibui]

Seedlings seem to be pre-programmed to grow new roots. I guess that's an adaptation to cope with all the things that like to eat plants and roots. Even species that are normally difficult to root as cuttings (like pines) can root as seedling cuttings so it is not surprising that JM seedlings can do it too.
When I pot up seedlings I often chop roots really hard because that stimulates lots of new lateral roots.
I'm also comfortable with potting on rooted cuttings any time they have sufficient roots so I'd certainly pot up these now.
I don't have to cope with Canadian cold but potting these up should not diminish their chances provided you give them normal winter protection