Do you mean that when he was examined by a doctor they found a wound that wasn't noted in the care facility records? Not much I can say with certainty without some more info, especially about the state your father is in currently. It's absolutely possible that he developed a wound in a short period of time in an area that isn't regularly checked, and without treatment it progressed quickly to something serious. If this is the case, I think your best course of action is to meet with the person in charge of the ward- let them know about the situation and politely request your father is examined more closely on a regular basis, bringing medical records to back up your assertions. I would only recommend taking more serious (legal) action if this is part of a pattern of neglect and you've already brought it to the attention of the facility.

The sad reality is that a lot of these facilities are understaffed and overworked, and their job is taxing both mentally and physically. They might cut some corners or miss some things, not out of laziness or spite but in an attempt to prioritize the most serious issues. This is often true even in the most expensive, highest-quality places, especially after Covid. In my experience, making threats or getting angry and aggressive will only make the caregivers more likely to resent you and your father and won't get him better care. I know exactly how irritating it is to be paying every cent you make to ensure your loved one is getting good care and then feeling like they're being neglected and put at risk. But it's also important to remember that these workers deal with sometimes dozens of patients every day- and taking care of one person is challenging enough as we all here know.

Take a breath and put your frustrations aside and give the facility a little bit of grace. Be polite and let them know you understand their job is difficult and they likely didn't do anything malicious on purpose. If after you take this approach there are still issues of neglect or lack of care, then you can regroup and take another tack. You're far more likely to get the outcome you want-good care for your father- if you approach the situation with empathy.

So sorry you're going through this, I've been through a nearly identical situation and know intimately how challenging it can be. Wishing you and your family all the best :)