Root rot is very possible. The sprinkler was accidentally left on too long recently. If so, is that wilted plant a goner?
I would pull - or dig it up and destroy it.
root-rot is a microbe (bacteria?) that multiplies
i would mulch the area, about 3ft sq,
feed the area with fish emulsion and molasses, (papaya plants will love that also)
and not use it till spring.
this will increase bacteria and fungi which will help out-compete the bad guys.
its possible you can save it, but they grow so fast from seed , IMO its not worth it.
every time i had a papaya i tried to nurse back from a serious problem,
it took several months... in that time, you can grow one from seed.
yep, they hate standing water.
if you really really want to save it, feed it like i mentioned
and cut the top off completely. it will reduce transpiration through the leaves.
the roots now can not uptake as much water as before, until it grows some new ones.