5-6 lights slowly moving in my pasture

I got up before 5 am MT on November 9th, 2018 as is usual for me.  When I looked out my window I saw several lights moving slowly down and around the hill in my pasture.  I immediately went outside to get a better look and indeed there were 5-6 separate lights that I assumed to be from UTV’s and/or ATV’s.   Knowing they had to be trailered in as there is no road access, I went back inside to get a coat, boots (there was a light coating of snow) and of course coffee before heading down the hill to see who it was. I was in no hurry knowing they couldn’t get out of there quickly due to the Badlands terrain.
Returning to the shop I took out the truck and I was now visible to them with shop lights on and headlights.  At this point I saw a much larger vehicle I assumed to be a big semi-truck, turn on its lights and it also had several amber “curtesy” lights above the headlights.  My intention was to go down and get a photo of the license plate.  About 30 minutes had passed and they were still out there.
They made no sound, were non-threatening and my dogs did not bark nor were the horses upset.
I then videotaped the lights on my phone which were still moving slowly around my pasture as if they were looking for something.  At the time, I believed they were “shining” for deer or poaching.  Not being able to drive directly down the hill due to the snow cover I went around to the back gate, which took about 2 minutes, to get a picture of the trailer they had to be hauled in on.  It was still dark but there was some moon reflection off the snow.  I found nothing at the back gate.  No truck or trailer, no tracks, nothing, so I went to the neighbors on the opposite side of the hill to see if they were parked up there.  Again, nothing.
I went back home and the lights were gone.  About 45 minutes had passed and it was starting to get light. I drove all around my property, about 10 miles or more, looking for tracks how they got in. Nothing.  No tracks anywhere, at any point, no evidence whatsoever that anyone had been in my landlocked pasture.
The only evidence I have are the photos captured from the video I made. The photos are of machines like nothing I have ever seen; nor any person I have shown them too.  I notified law enforcement and posted it on Facebook.