Edit: After detecting the error I closed OW. A little later there was a small patch, the missing skins are back now.
I played last yesterday and today I noticed that I lost the sinks and cosmetics I had already unlocked.
I also found this article from august 2018 saying that Blizzard knew about the bug and will take care of it.
(www) dbltap**(dot)**com/posts/6152844-blizzard-working-on-fix-for-missing-cosmetics-in-overwatch
That was almost 2 years ago now and the bug still seems to exist.