I would agree with this take. That is a long time and with Bitcoin's insane valuation increase, no matter how often people want to repeat it, 1 BTC does NOT equal 1 BTC. At best, you could probably sue someone and try to recover the USD amount, but I'm certain that wouldn't be worth the effort for you or you wouldn't have left it there in the first place.
The legal standard is usually where the party actually knew or where a reasonable person would have known that the access had been taken away. Damages would be limited to the value of the bitcoin at that time. -- which is presumably not much or they wouldn't have ignored it.
Of course, an ambulance chaser lawyer could no doubt be found that would take basically any case with the hopes of scoring a settlement payout for themselves well beyond anything deserved just to get them to go away.
I feel bad for everyone who has ever run a bitcoin service, now exposed to a lifetime of claims for increasingly absurd amounts... often over imagined balances that never existed or were withdrawn and forgotten. But even when they were real, over amounts that were inconsequential at the time.
I never did, but because I used to be listed on the website I still periodically get emails from people demanding and threatening me to give them access to wallets of bitcoin fortunes they claim they purchased in _2004_ or other impossible years. I can't imagine what it's like for people that actually did hold coins for others at some point. I also get insane messages because I was one of three potential signers on an escrow for a hack recovery bounty once, totally crazy.
Regarding unclaimed funds-- my understanding is that in most (all?) states those laws are not drafted in ways that apply to Bitcoin. Anyone who did lose a real amount of coins with a service ought to try drafting a kind letter to ask for them, you might get lucky. But be aware that that target of your letter is probably flooded with crazy threats and abuse, and won't want to help anything that looks more than that.
So you need to provide exactly the information to correctly identify your accounts and that you're the proper owner, and you need to be extremely professional and polite. Being abusive or threatening will absolutely not help, it will guarantee that the only way to get anything would be via legal process and as I explained at the front you're probably not owed anything significant according to the law.
