This might be a long shot, but is there anyway of finding flight results / general costs from a past date? I booked a work related flight using kayak.com for a flight a week ago. However, I now realized in order to be reimbursed for the flight by my employer, I have to prove that I booked the cheapest flight available for the date I traveled. Is there anyway to see previous flight search results? Thank you.
This is technically impossible. To get your employer convinced that you booked the cheapest flight you had to make a booking question for the past, but even if someone implemented such a thing, it won't give you the right answer: These cheap flights your employer wants to know about are now alredy booked by other persons.
This isn't possible, because airline tickets are dynamically priced: the price you see depends on a host of factors, such as current availabilty of seats. Also, the cost of a particular ticket can depends on who you buy it from, so being able to retrospectively find the cheapest ticket would require data from all sellers – it wouldn't be enough for, e.g., the airline itself to keep a database.
In practical terms, your company might be happy with an approximate price. For example, suppose you paid $500 for your ticket and you can show that there are tickets available today for $450. They'd probably be prepared to reimburse you the $450, which means your mistake would only cost you $50. Conversely, if the cheapest ticket today is $550, they might accept that your $500 was probably close to the cheapest you could have bought. Talk to your manager and/or the accounts department.