Other suggestions: Have you checked local Pawn Shops, Sales Ads, machine shops, chop shops, etc.? Also, I would be on the lookout, if the welder could be removed from the trailer, for what the lawn men using to pull their equipment.
Many illegals make their livings from theft. That's a way of life in their country, and they bring their ways with them, when they come here. How do I know? My church's Mission Board has made a report to that effect. Also, I caught a couple of illegal men in a stolen P/U, with plates from a different car, trying to steal my neighbor's trailer out of his yard. I just happened to be going out my front door, and one of them was knocking on the front door, calling out to them, asking if anyone was home. Everyone, even their lawn crew, knows that they are gone during the day, so something just struck me as being wrong. I stood behind my car with my hands on my hips, watching the man examine the hitch on the trailer. When they saw me, they left really fast. They were young, but they had a walker in the bed of the truck, along with a little kid's bicycle. So, I followed them around the neighborhood at a distance. It was obvious that they were cruising the neighborhood, looking for things to steal. Then, one of them went to the front door of a house and knocked. No one answered, so he took the lawn mower that was on the front lawn. I called 9-1-1, and followed them until the cops arrived, giving them a description of the P/U and license plate number. They were illegal, and the 9-1-1 operator said that was the way many of our local illegals make a living or supplement their living. They sell what they steal to local perpetual Garage Sales.
I second the recommendation to get video surveillance. Also, there are those cameras at Academy that take pictures of the deer, when they go by and trigger the electric eye. We have lights that go on, when someone goes by. You can also buy an alarm at Home Depot that will go on, when the lights go on ... either in the house only or outside, too. The camera systems can be found at Home Depot and Sam's, too. Don't rig up a gun to go off, because that's illegal ... however tempting it may be.
From my perspective, it is much more delicious a victory to become pro-active and set a trap/self-defense system for these BG's that will identify them to the Police. I'd have cameras all over the place to "shoot" them from every angle possible, plus alarms, plus lights. Now, that's the kind of shooting that would just thrill me to no end!
Think how great it would feel, sitting in court, as your evidence sends them away ... or, more likely, gets them deported.Being pro-active, also, helps to get over the bad feelings of being violated. It's the best cure that there is for the PTSD that follows something like what happened to you. Post Traumatic Stress does not have to be permanent or bad, if you do something to counter-act it. Working it out, like you are doing, in this thread is a good step.
Good luck!