Normally, you would see Google Posts show up in or near a local knowledge panel when you search for the business by name. Brodie Clark spotted Google testing showing a Google Posts without any local knowledge panel. Was it a bug or a test - I do not know.
He posted a screen shot on Twitter and shared more over here. Here is that screen shot:
Mike Blumenthal said he has seen this before but it has been a while. To me, it just seems buggy but what do I know?
Forum discussion at Twitter.