Check out www.leaktools.com. You can read about how leak detection works, repairs, etc. I bought my own set of tools to test my own lines. I think the high pressure broke something, maybe not right away, but jiggling the valve may have caused a "water hammer" that finished the job. If you are losing significant amounts of water, it's got to be going somewhere. If you can't see it, it's going into the ground somewhere. Good luck.