Have seen with 〜た+ことがある
Grammar Explanation: Previous experience with 〜た+ことがある

Sacchan and her friends come across a torn piece of paper with 「あたり100」 written on it. Thinking it may be for a 100,000 yen prize, the girls head to the shopping district to redeem it. Along the way, their friend Nonoko says she doesn’t recognize where the ticket is from, but Sacchan’s mother says it looks familiar somehow. Kotoha admits it seemed familiar to her as well, but she thought it was just her imagination until now.
- 結衣:
- 「私
( とさっちゃんとののちゃんは知( らなくて」- “Even though Sacchan, Nono-chan, and I don't know it...”
- さっちゃん:
- 「かーちゃんと琴
( ちゃんは見( たことがある」- “My mom and Koto-chan have seen it before.”
Key Points
見たことがある means prior experience
見
( たことがある says Sacchan’s mom and Kotoha have seen the ticket or something like it before.The pattern does not say they are seeing it now; it points to memory.
かーちゃん is a casual label
かーちゃん is a childlike way to say mom.