After starting and stopping the car 10 to 15 times, driving it, till normal temp, shutting it down, starting and stopping a few more times and waiting 4 to 8 hours between a few of the tests.

Since I pinched the hose to check for where the pressure loss was taking place, the pressure has and continues to hold.

There are 2 possibilities that I can see. 1. That it is such an intermittent problem, I could go a long time between symptoms showing up. 2. That when I was pinching off lines, in one test I was slowly pinching off the return hose, which raise the pressure enough to cause the hoses to begin to move around (maybe 60 plus psi) for about 1.2 seconds...and that might have cleared out something that was causing a problem.