I have done several tests on my own, but recently I was approached by someone wanting to test some ideas against me. Their proposal sounded interesting, and so I decided not only to post the results, but also to invite others to message me if they would like to run any tests.

+++++++++
Theory: Critical Hacks do not immediately show up as a scanned planet until you view the planet.

Test Conditions: Have a someone hack me until they achieve a critical hack. They then WRITE DOWN the name of the planet WITHOUT VIEWING IT. DO NOT CLICK THE BLUE HYPER LINK TO THE PLANET. They tell me the name of the planet and I go to probe it.

If the probe reveals no new scans, then the theory proves true.
If the probe reveals a new scan, then the theory proves false.

Battlefield Applications: If you are in a fight with an online target and you critical hack a planet, they will no doubt immediately begin probing their planets. The moment they find that any planet of worth has been discovered, they will Brick it, Temp Orb it, or Flux it. Thus you lose the benefit of the critical hack against an online player. However, if the theory proves true, then the attacking ship must show patience and discipline after the critical hack. By simply writing down the name of the planet, it allows you to go search for it later. In the mean time, your opponent has probed his planets and sees no new scans, and thinks all the good worlds are safe!

Theory Probability: Truthfully, I highly doubt that critical hacks do not immediately show up as scans. When we go on our scan runs, we don't stop to view every single rock, yet they are counted as scans and locked in our databases. However, I suppose it could be argued that we "see" the planet as we make the scan, but we only get a text message when we reveal the critical hack. It could also be argued that critical hacks work on the same program as shared planet alerts. Those planets are temporarily in our database, but they do not add to our personal scan history.

And the tests reveal:

They appear under recently scanned. I have hacked several people without stopping to look at the planet I critically hacked out of them. Then when I was done hacking, went to my recently scanned page to see what it was.

i have noticed that occasionally they do not appear in the recently scanned section, regardless if its worth taking then its most likely gone as soon as its hacked anyways

Ah but the real test was much less if they showed up in your recently scanned as much as did it appear as a planet scan to the enemy who was critical hacked.

just

it is the same as when you alert then purge. If it is an enemy planet it will go to an enemy scanned planets instead of recently scanned.