As that link says (unless it's far in the future when you read this and the link's dead), Sewickly's closed early in 2016 to make way for a new mixed-use building. It's since been knocked down. I've seen some of the demolition's progress. This afternoon I was out and about on buses, the last one being the # 14 back to where I live, and I rode it past what used to look like this:
...and is now rubble. With a hole, under where Sewickly's Addition, the diner part, used to be. And on the north side of that hole, I saw the outline of the stairs that used to go down from the kitchen area to that basement. Ghost stairs. Ghost stairs for a ghost basement.
I never went down there. Of course, neither did most of Portland.