sprinkler system sabotage?

I struggled for days trying to figure out why one of our drip irrigation zones could not be activated from the timer/control box. This is our first season with the system that came with the property, so I was assuming it was my own ignorance or worse, that we cut a wire during digging.

After reading the valve manual, playing with all the knobs, and poking around with a multimeter, I finally discovered that the green wire going to the solenoid valve was not connected to anything in the timer box. Conversely, the timer box's red wire for this zone was snipped clean and dangling free in the valve box. It wasn't stripped, so I don't think it fell out of a wire nut. A mystery, but it makes me wonder if the sprinkler technician who blew out the system for the winter snipped a wire to try to guarantee a spring service call. Well, it didn't work this time! It makes me want to figure out a way to avoid having to hire someone to blow out the system in the winter.