Thanks for taking the time to help diagnose the issue, much appreciated! Your diagram may not be accurate tho. Here's a picture of the situation.
View attachment 200328
I know for sure there is Romex under the grass along the perimeter of the driveway since when we moved in in 2005, there were pathway lights that we removed as they were damaged from snow plows. I removed the fixtures at the time, spliced and sealed the wire and all has been good for 17 years. I assume the Romex runs under the driveway in order to connect somehow to the switch in the house.
The coach light in the upper right stopped working a month ago. The only variable I am aware of in that month's timeframe is the sprinkler work, hence my suspicion that the culprit is the wire that is buried near where the sprinkler head was moved. I suspect I'll have to follow the wire a little more toward the house (since he moved the original head closer to the house) and see if there's another break.
I logged a call with an electrician in case I need help in the end. Waiting for a call to schedule a visit but wanted to troubleshoot as much as possible beforehand to cut down on the time he would charge chasing the break.
One of my concerns is that if I have to remove a longish length of Romex to do a splice, I'm not sure what kind of Romex to get, especially since as
@Patrick said the Romex in the ground is not suitable for that application. If I get UF-B and splice it in, would it be compatible with the Romex that's already there? Also, since it isn't a proper use of the Romex, would a licensed electrician be willing to simply repair it, or would he say it's not "code" and thus propose to lay a whole new wire ($$$$)?
thanks again for any insight