Hi everyone, sorry for the missing PressRow link in Appearance > Themes. It's back now. It was my mistake—had meant to only hide it from newly registered users and not everyone else.
When we replace PressRow (we don't have an exact time on that yet) we'll let you know in advance so that you have time to test out the replacement or try out other themes.
The idea is that you should be able to re-activate PressRow as you test things out and make comparisons. It will be available to re-activate until we make the final switchover.