Wow, unexpectedly your answer there solved the issue for me. Essentially I must have done exactly what you said. When first setting up my wallet and being prompted for the passphrase I had mistakenly interpreted it as “create a password for your wallet” and entered a password (twice, to confirm it). Unknowingly, I had then created a new hidden wallet on my Trezor. Entering that “password” now as passphrase does indeed restore the correct wallet.
Weird feeling how it goes from “I’m 99% sure I have done nothing wrong here” to that it was indeed a user error. This was one of the first few times I used my Trezor T and I must have been unfamiliar enough with the Trezor connect window to misinterpret it as related to the wallet and it simply asking for a password. (Had I seen it today it could never have happened). I saved the password, but in my memory I had only pre-created it and never used it as a Trezor connected wallet doesn’t require a spending password (“I made this password but I know I never used it”). And I knew I only had one single passphrase that I had knowingly used on my Trezor, so the idea of me having typed a wrong one was simply not there. But turns out it was indeed an inexperienced user error after all.
Well, that is a relief. Thank you very much for your help!
For anyone else with the same issue, try entering any password that you might have used when creating your wallet as your passphrase in Trezor, you might have created a new hidden wallet without knowing it.