Thanks for sharing. I always enjoy learning from these types of experiences. One thing I always do no matter how trivial of a script I run against a production database is to wrap the entire script in a transaction as follows:
BEGIN TRAN
DELETE FROM table WHERE id = 5
ROLLBACK
This allows me to see how many rows are affected while performing a safe operation. If I see "1,000,000 rows affected." when I'm expecting 1 row, then obviously something is wrong and I probably just blew out my log file. If it does work as expected, then I simply swap out the ROLLBACK for a COMMIT or exclude the BEGIN TRAN and ROLLBACK lines from the batch which will auto-commit. This has saved me from many unexpected and potentially epic fails.
Please keep in mind that this won't completely ROLLBACK all changes in all scenarios but in general, it's a good practice.