This was very likely a Google server error. Here are some details and the solution.
This started at 8:55pm EDT (GMT -4) Friday, October 27 and continued for almost 3 days when I stopped waiting for it to fix itself like the last problem I commented on a few weeks ago.
Nothing had changed in 17 days such that I should lose access. The script was most certainly still there. Everything involved was owned by "me."
What may have triggered the problem is that I set one of my libraries--not even the one that "broke"--from developer mode to fixed version mode. At that moment, Google lost data.