cinderella –
I don’t want to get into technical halacha discussions here, but here are some facts. The is an opinion out there that pas akum and bishul akum are not a problem with packaged goods from a company (since the only issue is that they will lead you to become friendly with the goyim and in with packaged goods from a company that’s not a concern). There are other reasons as well.
The thing is that a lot of Hersheys stuff are kosher so for them to say that something isn’t there must be a reason. Right?
For one, OU’s policy is not to rely on certain halachic leniencies. Her rav might hold there is no reason not to.
You didn’t do anything wrong. You were following what you had been taught, and it’s impressive that you thought to be mekayem the mitzva of tochacha. I’m just giving you some info for the future, that there are perfectly valid opinions out there which say that reading ingredients is fine.