A paradoxical warranty

The world is void of trust

So the water pump went out on my car so I went to the parts store to buy a new one. When I bought the part I asked about the warranty on their water pumps since faulty parts are very real things. The cashier told me that it had a lifetime warranty as long as I could prove that the system. As I was driving away from the store I asked myself how I could possibly prove that the system was flushed. If I told them that I did it myself they wouldn't believe me, but if I took my car to a mechanic to flush the system I'd have to pay them a bunch of money, which of course defeats the purpose of buying your own parts. Not only that but how could I possibly trust a mechanic to actually do the work that they said they did? I care more about my car than any mechanic ever will, they only care about getting paid, there have been times where I have had to fix the mistakes of lazy mechanics who worked on my cars, and I also know of people who have gotten into deadly car accidents due to their cars malfunctioning after their mechanic didn't do what they said they did. The parts shop can't trust me to fix my car right and I can't trust a mechanic to do it either so I guess this warranty can never be satisfied.

I really do think that this is a ridiculous warranty. The type of person that would go into a part shop to buy any car part (especially something like a water pump) is the type of person that would more than likely do it right. Car parts shops should have more trust in their customers.