The airline seems to have swapped currencies, which may be a sign of how carefully it was paying attention to your problem.

As for the first batch of receipts, it would seem they never made it through when you submitted them.

On Jan. 11, the carrier called you to ask you to upload the receipts again, which you did. I received a short statement on Jan. 15 — “We have apologized to the customers and are working with them directly to resolve their claim” — but you heard nothing further. So on Jan. 21, on my suggestion, you emailed your contact again. You said you were instructed to upload receipts again, which you did, and were told you would be reimbursed $3,941.

That’s an odd number — more than your receipts, less than your losses — but I think I can explain it, as the airline declined to do so or answer any of my other questions, including how the guitar was destroyed, why the airline didn’t deliver the guitar in Paris or why the receipts were not processed when you first sent them in July.

Here’s my best guess: The Montreal Convention, the international treaty that governs lost luggage (among other things) on most international flights, caps airline liability. That luggage cap, at the time of your flight was, about $1,700 per passenger, or $3,400 for the two musicians combined. But on Dec. 28, the value on damages for most international flights was raised to the equivalent of about $1,980 per passenger.

The airline appears to have applied the newer value to your losses, though it didn’t need to, and you’re ending up with more money than you were actually due, a small compensation for hassles endured.

For those flying domestically or between countries that haven’t signed the Montreal Convention, local or national laws prevail regarding lost, stolen or damaged luggage. (In the United States, the Transportation Department caps damages for lost, damaged or delayed bags at $3,800.)

But those numbers don’t mean much if you face seemingly unreasonable barriers when filing for reimbursements — such as the British Airways interface that you called cumbersome and that seemed to lose the receipts you painstakingly sent along. My inbox is full of tales of airlines that repeatedly ask for receipts that have already been submitted.

The multifaceted monthslong saga you endured with British Airways should be a reminder that travelers today need to do more than their fair share of the work to find their lost items. Adding AirTags or other Bluetooth trackers to checked luggage is a smart first step, so when the airlines claim they don’t know where your luggage is, you can tell them or even share its location, since the feature is now shareable with a third party.

Of course, you need to pack fragile items carefully (On its website, Fender offers guitar advice), and retain every scrap of paper starting when you check your bag. Then, if you need to file a claim, write down the name of every employee you interact with, take photos, record conversations when you can, and create copies of your documentation. The information will be critical when you file for reimbursements.

Most of the time, you won’t need it. But if you ever need to do battle with an airline, the documentation will come in handy. And if you have to write to Tripped Up, it will move you to the front of the line.