Obviously your current wallet is no longer secure and you should move all your coins to a new wallet.
DO THIS 
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There is no point backing up your seed phrase and passphrase on the same piece of paper, since then the passphrase is adding nothing.
That's not entirely true: this scenario still protects you against a $5 wrench attack: the password gives you plausible deniability if the Trezor also shows (much smaller) funds when used without password. But indeed, the password doesn't protect you against an attacker who finds your backup.