Thanks for your suggestions. A few quick notes in response:

1. Unfortunately, Chase won’t reopen the case since it’s already been closed three times. If anyone knows a way around this, I’d love to hear it.
2. I’m not sure if it’s possible to just email the airport for an official record, but if anyone has experience or knows the right department at TLV to contact, please let me know.
3. This was on a Chase Sapphire Reserve, so it technically has travel insurance. Honestly, I expect the adjuster will be more than happy to close out the claim for lack of sufficient evidence, but I’ll give it a shot anyway.
4. You’re right that the airline does operate charters between TLV and ATH. I actually looked up both of the tail numbers registered to that airline, and on the date in question, neither one flew that route. So it wasn’t just a canceled flight—it simply didn’t operate that day.

If anyone has more advice or knows a different way to escalate, I’m all ears. Thanks again!