、。
She bought a handbag and lost it the very next day.
Literal
She [topic-は] handbag [object-を] bought [but-が], that [of-の] next-day [on-に] lost.
翌日 (よくじつ) is a Sino-Japanese word for 'the next day, the following day,' more formal than 次の日 in everyday speech. The combination その翌日 ('that next day') anchors the second clause's time relative to the first: 'the next day after she bought it.' The clause-final が here doesn't mean 'but' in a contrastive sense — it's the soft connective が used to set up an unfortunate or unexpected follow-up event, similar to a sigh-marker between clauses.