The question you are asking isn't really a Fortinet-specific question. It's a general cybersecurity question and no one here can really answer it for you. It depends on you and your environment and whether you need to know those details or not and what kind of risk appetite you have for something like that (or worse) happening again.
For example, if you just wipe the device and re-install, whatever attack vector existed before likely still exists.
Up to you really how you want to approach this, though.