The US had a "first to invent" method of resolving priority for patents, until the 90's when it adopted the "first to file" method used in most of the world.

The "lab notebook" like Hoerni used was crucial to establishing that you really did invent it before someone else, even though you didn't file for a patent yet. This was tested in an "interference" proceeding. Naturally, bureaucratic procedures are the closest thing to eternal life that we have on Earth, and they still exist:

https://www.uspto.gov/web/offices/pac/mpep/s2301.html

Given the infrequency, cost, and complexity of interferences and derivation proceedings, it is important for the examiner to consult immediately with an Interference Practice Specialist (IPS) in the examiner’s Technology Center, see MPEP § 2302, once a possible interference is identified.

"Infrequency" -- they got that right. The vast majority of patent practitioners have probably never done one.

Not only was Jean Hoerni an inventor, but he was also a (grumpy) philanthropist. His financial contribution to building schools in Pakistan is discussed in Two Cups of Tea.