The brake controller I have in my truck,'Genesis' brand, flashes "OC" (open connection) for quite a bit after I unplug any of my trailers with electric brakes. I'm sure you could wire in an audible alarm(or have it done for you) to let you know your trailer's wiring harness has come disconnected.
It doesn't take long at all to wear down a trailer pigtail @ 65mph. I've let friends borrow trailers of mine and return with something that looks more like a $30 wedge to hold a door open than an adapter.
You might want to try an in line wire conntector with a shrink tubing heated over top of the connector. Make sure your shrink tubing is on the wire before making your crimps and that the tubing fits over the connector but isn't too wide that it won't shrink down onto the wire. Splice and crimp your wires, slide the tubing back across the connector so it overlaps onto the wires an inch or so and heat it with a flame... sealed.