What do you mean by this? What aspects of their conduct would someone need to be secretive about?
If the patent, on review in court, fails the originality, novelty, or lack of prior art review, the patent can be dissolved.
https://www.retaildive.com/news/newegg-the-bane-of-patent-tr...
https://www.newegg.com/insider/newegg-vs-patent-trolls-when-...
A patent filed on a prompt would most likely fail the novelty/prior art review phase of the patent application, so the only way a patent could succeed being granted in the first place would be through extreme secrecy and probably bribery of a patent agent to push the patent through.
Just because you have the patent does not mean you will win all infringement claims though, as you noted with those Newegg cases
If your patent is crap, like the one that could feasibly be put on a prompt, then there is only the thinnest veneer of protection for your prompt idea, so it's pointless to make one if there is any value more than the 10-30 lawyer hours needed to take it to court and destroy it.