Nothing?  What else can I do?  My crypto is gone, I cannot transact with zero cryptocurrencies.  Aside from figuring out why it was gone,  I would follow with the best answer I guess... 


In addition, I will reformat everything and if possible would put another layer of security in my units (computer, gadgets, and room).  And improve the way I secure the backup of the seed phrases and keys. 

Exactly! That's the point i was trying to make. We never know. Things can happen.
Just like you would have never known in 2020 that there would be a war in Ukraine. (don't criticize, just a figure of speech, you get my point).

It can you that on day a backdoor/vulnerability is found, and some wallets got swept. And you happen to be one of them.

You never know.



[/quote]
I have no idea what would I do if a situation similar to what you described happened to me, but I think that my first reaction would be tearing my hair out and running from corner to corner like a crazy person. But a situation like that may happen to everyone, even with those who practice good opsec because one day a critical vulnerability may be found that will allow hackers to empty all wallets, including ones created on an air-gapped computer with good random number generators. Hopefully, the open-source and decentralized nature of bitcoin development will enable developers, contributors, and reviewers to catch such bugs very early and take all necessary steps to minimize the harm.
[/quote]

Not sure if I'd share the same opinion. While not storing all your bitcoin in one single wallet will decrease the chances of you losing your holdings in one unfortunate event, it increases the chances of you losing a part of your holdings.

What you mean is also true, If someone stores their Bitcoins in a hardware wallet and practice good security it will be difficult to get in and steal all the Bitcoins in it.
And I also believe that if an investor has a very large amount of bitcoin, they will dare to spend a little money to be able to guarantee security for the bitcoin wallet.
It is impossible and unreasonable for someone to store large amounts of bitcoins in just an ordinary wallet.

Regarding OP's stated scenario, If ever I'd be waking up in one morning and see that my funds are gone, I'd probably check the transactions and if it is transferred to another wallet who I'm not familiar with, that would be it. Acceptance would be the only way out as well as knowing what could have wrong. I won't hope that funds will be returned especially in this industry. Best way is to just learn from it even if it is not an easy thing to do.
Regrets and frustrations won't be helped especially if you've lost something that important. But as I've mentioned, knowing what could possibly go wrong would lessen the burden especially if you are at fault for such instance. And if not, try seeking for possible reasons why such thing happened and try to contact the management of your wallet to somehow see what can you do to simply help oneself.

There's always an entry point, a vulnerability, an exploit.

Say you do follow all the safety advice. You have funds divided into a number of wallets, you hold everything offline, you have backups, you don't store your passwords anywhere... What was the vulnerability? Did you let someone into your house? Was the backup physically taken and uploaded by the attacker?
I hold a lot of BTC and most of it is at least 5 years old. I've never had anything stolen from me and I've never had any type of security breach, that said, my friend had ransomware on 2 of his computers. I know people who had USB stick trojans that they got by using public printers and stuff. I had that malware that changes your address when you copy-paste on one of my "online" computers.
Everything can be found and cleaned once you are aware that you could be infected and take certain measures to avoid spreading it to your cold storage.

What if I wake up one day and it's all gone? I'll lose 80% of my liquid funds. I won't be forced to beg, or live in a tent, but I'll lose the ability to buy expensive stuff and invest for many years, maybe forever. That's why I make sure I run a tight ship here ant there's security layers over layers. The only way I could lose it all is if blockchain itself was compromised, but that's something I have no control over.

I don't think I'll be able to do something, I'm holding everything in OWNR wallet. I can check transactions on the blockchair, but everything is anonymous, it's not possible to find out who could do that. The only way someone can steal my crypto is to steal my seed phrase.