I've bought emerse Anubias a couple of times in the past and usually some Anubias ends up dying. I don't bury the rhizomes into the substrate, I just cram it into the nooks and crannies of the driftwood or tie it down. What happens is the leaves and stems just float away and the rhizomes turns into mush.
Was the rhizome yellow? The only anubias from a tube that melted on me was coffeefolia and the rhizome was almost all yellow. Months after it melted the rhizome is looking more green like the other established barteri and sprouted a new stem with a small leaf. The leaves were at least 7" long when I got it, now it's 1 stem not even 1/4 in with a small leaf and for months hasn't grown beyond that.