Yes, if it happened then the hard forensic evidence is gone forever. The only remaining evidence would be witness testimony, and if anyone even remotely credible ever says a word they will be destroyed. So... yeah. The world will never get a solid answer on this one, sadly.
It has been more than a year since SARS-CoV-2 began spreading in China and the WHO is still too busy cowering to state that it originated in China. That's the first pitch of the first inning and they can't even do that. It's absolutely a safe bet the zero-credibility authorities will never provide an answer as to the origination of the virus. Their entire obvious goal is to never - not under any circumstances - blame China. They still dodge and evade that at all costs. They've collectively humiliated themselves and should be mocked frequently for it, for a long time. Every other sane person already knows where it came from: Wuhan, and likely inadvertantly escaped from their biolab after having been sampled from bats. It's the only credible, rational explanation given what is known (including about their sampling program and horrific lab security); every other explanation requires farcical, laughable stretches to go far out of the way to avoid blaming China (it was India; it was imported via frozen food; it was the US army; etc).
The job of the WHO is not to hold member states accountable during a pandemic, it's to provide support, services and intergovernmental collaboration. To share learnings. To provide their expertise to those involved. It's to provide health care to the poor and to share understanding.
They're not "cowering" to a country that provides them a teensy tiny fraction of their operation budget. Not to mention, they're not the "Health Police," they're doctors and epidemiologists.
The WHO has a ton of credibility. They've only been mocked by people spreading misinformation guided by their personal political beliefs. They certainly aren't the ones humiliating themselves.
If you want someone to hold China accountable for... honestly, there's no clear evidence the state of China did literally anything right now... take it up with the UN Security Council. You don't get mad at your doctor for the flu existing, and you don't get mad at the WHO for doing their jobs.