I’m assuming these fuyu are grafted on American stock and the graft is just at the soil line or below:
I would cut it down just to above the graft and hope you get the American native stock to sprout/ or sucker. Wait until the native stock is sizable to graft and graft some more Hardy hybrids.
I’d like to find out who or what nursery told you that you could grow Fuyu persimmons in zone 5.
It will not even survive zone 6 where I am. I used to see a local nursery near me selling Fuyu to customers who were unaware of the tree’s zone limitations.
You need to be in zone 7 or higher to grow this persimmons in ground unprotected.
My assumption is that you only have the rootstock remaining and you’ll want to pick the most vigorous shoot and start over next year (with cold hardy options). Welcome to the forum!