What you describe here is "change address", and that would only affect the overall balance that Trezor displays, an example of that would be your Trezor showing balance of 1 BTC, and then when you copy your current address to one of the blockchain explorers it would show 0.6BTC, that missing 0.4BTC belongs to a change address that was created when you made a transfer from your wallet at some point in the past.


OP's problem if I understand it correctly isn't related to that, he mentioned a missing output, so this means, the balance on the explorer is larger than what shows on his Trezor.