If there is ever a legal battle over the location/boundaries of a claim the physical markers/posts take precedent, then the written description on the location notice.
Absolutely correct as stated.
Actually in legal practice the certified County Recording is prima facie evidence of the true location in court and unless that evidence is challenged the monuments and markings on the ground do not come into play. It's only when the legal description on the location notice is unclear or challenged for accuracy the monuments come into play. Just as with prospectors looking for open ground the location notice establishes where the claim can be considered to be found but boots on the ground to see the actual monuments is the final word on where the claim is in fact located.
Why GPS or maps are not used very much for legal boundaries is most likely because the legal process for staking claims very old, before the days of GPS and hand drawn maps were the norm and they can still be used. Apparently, no court, agency or county has seen the need to change the old way of doing things so what we got is what we got. Call me old fashioned but I would just as soon leave it the way it is. New regulations scare me! You think it is bad now,,,,,, "I am from the government and I am here to help."
"No court, agency or county" can change that law. It's found in the Mining Acts themselves. Only Congress could change the legal method of describing a mining claim. States and Mining Districts could
add other requirements (and have) but the basic requirement to locate by the PLSS or metes and bounds can not overruled by those States and Mining Districts.
The PLSS system and metes and bounds are more accurate than GPS. Both the PLSS and metes and bounds are tied to local physical permanent objects. Commercial GPS unit locations are are only 98% accurate to 30 foot. Local surveys tied to physical objects can be extremely accurate. GPS coordinates are not a legal land description. The latitude longitude system is much older than the PLSS so actually GPS is less "modern" than the required location system found in the mining acts.
Take pictures, document anything and everything, it is up to you to protect your investment. Send the pictures to BLM with your paperwork

Might be a waste of time, they will most likely get filed in the round file.
As I'm sure you know your location notice at the County is the only certifiable record of your claim. That record should be as complete as you can make it. Including photographs or affidavits of witnesses as well as any additional information about the location is permissible. That location notice is your public record of your claim of right.
The BLM only receives a courtesy notice of your location. That legally required filing is not a public record and can not be certified to a court. Include all the same elements of your original County Record of location but don't expect the BLM to get much beyond the quarter section description on the front page. There are several important court cases instructing the BLM to review the entire claims case file when they have a question but they continue to ignore those instructions and rely on the first page.
CA BLM has included a "suggested form" for your Annual Assessment Work and it includes section "5. The undersigned testifies that on this date of _______ all monuments required by law were erected upon the subject claim"
The "suggested form" is most often incorrect. Last year the suggested Annual Assessment Work form for California
was rejected by at least one County Recorder for being legally deficient under State law. The BLM offered a suggested form for location notices in Arizona for many years that didn't even meet the basic requirements for a legal location in Arizona. There are many other instances of the BLM offering "forms" that could cause you to lose your claim.
The BLM does not keep legal records of claims and they are not in charge of defining what forms should be used with one exception - the 3830 Small Miners Waiver declaration. The BLM is not your friend, not your lawyer and not a reliable source of information. Add what you wish to their files but as you pointed out they might just round file anything they don't like.
As for monuments being vandalized or destroyed - the cost of replacement put this firmly in the puny misdemeanor category. Without really good evidence of who vandalized the monument and when you are pretty much stuck with replacing the monument and moving on with your life. If the destruction was because of a dispute with another claim owner then you have a civil matter and you can sue in County court and get your costs as long as you have proof that will stand up in court.
Don't sweat the little things. People get killed arguing about a small nugget or where a claim line is. Adding more stress over a club claim that only gets mined intermittently just leads to more stupid media stories pointing out that miners are ignorant and dangerous destroyers of nature. Not true but why give them the chance?
It's a freaking post, get another and move on, this happens to hundreds of claim owners every year. Whether it was a Californicator or an elk that destroyed your post doesn't really matter in the long run. Looking to the feds to get involved in a downed claim post is, in my opinion, a symptom of the attitudes that have lead to the government poking their noses into everything we do. I for one don't want the government federal, state or county to solve my mining problems. Another miner asking for the feds to help enforce the miner's duty to keep their claims marked is just asking for trouble much greater than a missing post. Beware you might just get what you asked for and more.
Heavy Pans