It is not possible for your return to be amended without your knowledge (unless someone gains access to your account.) At least not in the formal sense of "amended" that entails filing Form 1040X.
Can you give us a little bit more information about what you are seeing and where so that we can better assist? Has data changed when you login to your account? Did you receive a notice from the IRS that an item was changed? Is it just that your refund differed from what you expected? Any of these things may seem like an amendment of sorts, but require different methods to sort out.
Let us know a little more about what you're experiencing, and we will be glad to help!