つもり marks the speaker’s conviction for having done something when following a past-tense verb.
This is used when you thought you did something, but you actually didn’t.
- Jay Rubin. “Tsumori and the Vanishing Beefsteak.” Making Sense of Japanese, Kodansha, 2002, pp. 101–103
- Makino, Seiichi and Michio Tsutsui. “Main Entries.” A Dictionary of Basic Japanese Grammar, The Japan Times Ltd., 1989, pp. 503–506
- “2) verb ta-form” How to use つもり ( = tsumori) (maggiesensei.com)