Considering that having reported the problem, and then diagnosed it and proposed a workaround in Post 9 of this thread on 20/11/2019 almost 3 months ago, one has to wonder what is taking them so long. Just very low priority I guess.
It would seem it's taking the developers a while to complete the work necessary to implement this across the platform. I've been chasing it weekly with the product manager and as yet don't have a date for completion.
I concur that the icon has re-appeared on at least one of my PCs which previously had lost it.
It has also replaced the one on the PC where I had implemented a workaround.
It is recognisably different from the one which previously went missing, as it does not have the words "TalkTalk" on it, just the padlock.