As no one's even commented on this, I'll try to answer. Unfortunately that answer is something of a non-answer, because I don't think there's a better way (other than keeping better track of your finances in the future :-) ). There's no "universal clearing house" for recurring transactions (at least in the US, and I doubt other countries, but if you're not in the US, please note that), in fact only one party to each transaction even knows it's an automatic recurring transaction. While you can use some technology to help, such as downloading csv or PDF versions of credit card and bank statements and using tools like Excel or even grep/awk/perl to search them, it still comes down to searching for such transactions.
Also, while my paranthetical above was something of a joke, it's not entirely. You should at least be looking at your various financial statements each month and making sure you recognize all the transactions. What if someone copies your credit card number and CCV and starts using it? Examining your financial statements would also allow you to identify charges you recognize but no longer need.