Ya you only have a couple options. It's unlikely Hyundai will do anything, as you mentioned, since there isn't signs that would indicate it just "flew off" as you were driving down the highway....
You could go through your auto insurance, report it as "vandalism" - maybe go as far as calling law enforcement.
Problem is, it MAY be too late now for that, since they will ask when you first noticed it, and why did you wait this long, (Sorry officer, I had to ask on an online message board? hehe). Similarly, the insurance company will likely ask the same thing.
And yea, then you have the possible repercusion of increasing your rate for the claim upon your next renewal, and if you decide to switch insurance companies, you WILL have to disclose that yes you've had a claim within the past 2-5 years (depends on the company/form, some ask 2 years, some ask 5 years, after that it's all history; clean slate per se).
But yea, may just be better off checking a junk yard