I think there’s a good chance people will be looking for this now so will get caught a lot quicker next time.

That’s pretty much guaranteed from now on, yes.

It feels like the kind if thing that someone, somewhere would have a script running constantly testing for private keys with low values. That it went 18 months without being found is a miracle!

It’s not the kind of thing you’d expect to need to guard against, or even really think of. It should not happen. It sounds like someone was kind of just fooling around with making private keys and stumbled upon it.

I guess now someone needs to try seeding some of the most popular PRNGs with 0-255 and seeing whether any keys come up in the first few hundred numbers.