Google recently did a major upgrade on their crawlers.  When indexing a web page, what used to take roughly 4 days to index now happens in less than 30 minutes.

I use ahrefs for my business.  I can track trending topics.  For example, sonos, smart lighting, etc.  Each morning I get an email that shows me everywhere on the web it was mentioned.

In your case, If I put a keyword of "39 cent Stamps".  I'd have this post in my email by tomorrow morning. (and that's not even google).

The issue you're going to have with your test is it's such a popular topic, that your post will be buried under everything that deserves higher ranking.

To really check...Do something where you're talking about nonsense.  For example, chocolate unicorns riding bicycles.

Then you'll be able to locate it relatively quickly.  In fact, now that I typed "chocolate unicorns riding bicycles".  You can search it.