Cannot find a leak...it's been 3 years!

I have had my lines pressure checked by the pool company. I have also had my liner swam by American Leak Detector and another pool guy off found off craigslist. My pool is all the way full each spring where it is almost overflowing. As soon as I start up my pool it drops about an inch each day. I have done the bucket test for each of the last 2 seasons. I lose an inch each day on average. My summer water usage goes from 800 to 6000 and I never water my lawn. During the drought my soil cracks everywhere except in the lowest part of the yard where 1 or 2 inches appear starting about 2 weeks after I open my pool and then goes away in the fall when I close my pool. It seems my pool leaks more when the filter is shut off overnight. I never lose prime in my pump and don't see any air bubbles. Does anyone have any clue how I can find the leak? American Leak charged me $400. Pool company charged me $150 and the craigslist guy charged me $135. Another pool guy wants to pull my liner and look for the hole. I do not believe there is a hole in my liner since all fall, winter and spring I lose nothing. It is not leaking from my filter since it is on the other side of yard from the standing water in the soil and it is dry down deep. My guess it is in a pipe on the return closest to the where the standing water is. Is it possible that 2 companies failed to improperly test my pipes?