Cliff,
Some questions for you on the water hole...
1. Where is your main sprinkler box located in your yard? Is it near that area?
2. Are your sprinklers running off of your septic tank?
I'm not an irrigation expert by all means but we a similar issue...
We had a constant wet spot in our front yard and our sprinkler guys came out multiple times and said they didn't see a leak where I was concerned but the area stayed soggy. So I didn't water that area for two weeks and it was still soggy. I pulled up the sod and dug a little bit and saw water still filling the area. So they came back out again and there was some sort of issue not far from the main box with the main sprinkler line. I can't remember if it was a cracked valve or what but they finally got down to the root of the leak. They ended up having to dig deeper to find it.
If if you said it filled back up after running your sprinklers then I think the irrigation people may need to do a bit more digging cause that sounds like a sprinkler issue in my mind. Good luck and hope it gets resolved!!
I do recall them saying that sometimes those parts go bad off of the main line so he ended up putting one of those green canisters with a lid around it so in the future if it goes bad again there's access to it and you can see it fill with water. Not sure if any of this will help but thought I'd throw it out there for you!
Thanks,
D