Puzzling irrigation leak

Again back to irrigation issues.  WE've had a leak that we have not been able to find for a long time now.  We could watch as the irrigation pumps pumped water out from the lake but we could not find the location.  The rain made it even tougher to pinpoint a wet spot.  Well we finally found the leak and were able to make the proper repairs.  Take a look below to see where the pipe had burst.

Looks like an obvious wet spot.  Should have been easy to find right?

Zooming out shows a lot of weeds and debris near the sprinkler

The spinkler is located in there

Near the base of that power pole is the sprinkler head

 

This was obviously an old sprinkler that was left during a renovation.  It was nearly impossile to find because it was on any plans and had not been used in probably 15 years.