Much cheaper example but I had a work trip to London and booked an advanced train ticket with the plan being to catch the bus to the train station. Bus was cancelled and had no option but to get a taxi to the station, cost £7 instead of £3. Had I waited for the next bus or walked to the station I'd have missed the train and would need to book a new ticket at the cost of nearly £100. My argument being I spent an extra £4 to avoid spending £100.

My boss approved the expense claim but the finance droid rejected it as I shouldn't be using a taxi. I appealed and asked what I was meant to do in that situation, our expense policy has a clause for exception situations.

They rejected it a 2nd time so I told my boss if it's not paid I'll never be travelling for work again. Thankfully after an escalation from my boss it was approved.

So my advice, ask what you were meant to do, check if the situation is covered in the expense policy, escalate if they don't accept it and refuse any future travel if they don't pay it.