Wet rockwool insulation - HAS to be replaced?

Help please.
Short version - some of the rockwool insulation in my roof got wet. Should any bit that got wet be removed, or can it stay if now dry?

Longer version - water had been dripping from an old chimney that's had a section removed (from about 40cm above the joists, with the remaining chimney sitting on steel bearers - apparently a method no longer used). Rain has been dripping down the remaining chimney.
From dried out water marks on the topside of the plasterboard ceiling, this looks like it's been going on for some time.
All the rockwool that was sodden and dripping went straight into a bin liner. Other bits that only had a small amount of water I didn't remove.
By chance a wet trades guy (who came to quote for some rendering) said I should get rid of every bit of insulation material that got wet as it will grow mold with black spores.

What do you recommend?

And is there an itch-free substitute for rockwool that's as good?

Many thanks!
Mary

Mary,
Remove all semi-wet or even damp rockwool - why take a chance on mold.
What ever appears dry then why not lift it and check that it is totally dry?
There are lots of other kinds of insulation suitable for a loft - just google for them.

Photos of the bit of a stack on the roof, and pics showing the chimney breast inside the loft & showing water marks/wetness would help.