Your organized flight has been canceled. Write a letter to the airline company. You should 1) complain about the situation, 2) request what you need from them to make a travel insurance claim, 3) suggest what they should do in future situations.
Hi Delta Airline,

I am Ao Ni, I send this email regarding a cancelled flight of mine and to request documents to claim my travel insurance. 

I just received an email from you that my flight from Las Vegas to New York today at 10 PM was canceled due to mechanical issues. Even though Delta Airline will refund me the cost of flight ticket, the last minute ticket for tomorrow's flight is extremely expensive, almost double the normal price. I have to get back to New York by tomorrow to attend a very important meeting so I have to pay for the ticket, plus one night stay at a hotel for tonight. 

Will you reimburse my hotel and ticket? If not, I will have to claim it through my travel insurance and I need two documents to support my case. First, the confirmation of my order. Second, I need a letter from you to state the reason of the cancellation and that Delta Airlines is not able to reimburse my loss. 

I understand that bad things happen sometimes but I am still annoyed by the last minute notice. You should have noticed me earlier so that I could have had more time to deal with it. 

Please let me know if you need anything from me. You can reach me at 123-456-7890 or my email 123@gmail.com.