Speaker's conviction with

Grammar: Unexpected » 〜た+つもり

After a past-tense verb, つもり can say that someone acted under the belief that they had done something, even when reality differs: “thinking that I had ~”.

Further Reading

Examples

Suppressed presence with 〜た+つもり

Learn the meaning and usage of the grammar 〜た+つもり in Japanese, with examples from manga.
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While changing into her uniform, Rize hid in the closet when she sensed someone unfamiliar nearby. Cocoa, feeling as though she was being watched, opened the closet door.

ココア:
下着(したぎ)姿(すがた)の…ドロボーさん?」
“A burglar… in their underwear?”
リゼ:
完全(かんぜん)気配(けはい)(ころ)してたつもりなのに」
I thought I completely suppressed my presence, and yet...”