I'd do like you and try to find out when the surveyors are there, camera will work great for that. Also, if you could find out the surveying company, that would be even better. Not sure if your area is like mine or not, but around here all of the surveyors know each other. After they are done surveying, you could reach out to your surveyor and see if they would check with the neighbor's surveyor to find out what they came up with. If the neighbor's surveyor finds an indication of who surveyed the line before, they may reach out to your surveyor anyway and may reference them on the survey given to the neighbor.
As an example, I bought my land a few years ago and had a copy of the survey from the former owner, which my legal description was based on. One line had been apparently ran wrong by multiple surveyors in the past, since there are three existing pins within 10 ft of each other. The survey I had showed that line referencing a neighbors survey, which actually worked 10ft in my favor. That was the recognized line by the neighbors, which i was good with. I was able to track down the neighbors surveyor from 20 yrs before (now retired) and asked him about it. Weirdly enough, he remembered the property and why they were having issues lining it up. My surveyor knew the neighbor's surveyor, so he had reached out and discussed with him. They agreed and my surveyor used the neighbors survey as reference and cited him on mine.
I actually went out to the guy's house and he gave me a copy of the neighbor's survey that he ran with the line in question and put his seal on it. Was very grateful to him that he did so, since that should clear up any issues in the future. The neighboring land is in succession, and will most likely never be sold, since there are so many owners. Just didn't want an issue to crop up later, when someone gets a wild hair. Ended up costing me nothing, just did a good bit of research and had some helpful surveyors.
Who knows, you may be able to get a copy of their survey through your surveyor. Worth a shot...
Feel your pain, boundary/trespassing issues are no fun. Hoping it works out for you and you can get the issue put to bed.
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