Welcome
Was it just the binding/locked up feeling that makes you think you were in 4LO?
Given the design of our transfer case it would be nearly impossible for it to shift into 4LO on the fly/at speed. The shear mechanics simply wouldn't allow it. As mentioned, there is a speed (<2mph) and transmission neutral interlock to prevent people from trying or accidental attempts but even a software glitch wouldn't let you just slip into 4LO.
However, you can (and it is perfectly acceptable to) switch to 4HI (or A4WD/Auto) on the fly BUT to be in 4HI in our trucks
requires truly slippery conditions: ice/snow covered roads or being in sand/gravel--just wet roads aren't enough. If you were testing or the transfer case was inadvertently shifting into 4HI in dry conditions due to a flakey switch then the drivetrain will bind up. On the highway or straight-ish roads it can gradually feel like the whole truck is dragging an 18-wheeler and steering gets brutish but usually isn't too dramatic. Once you start maneuvering (like in a parking lot or pulling out of a driveway in particular) the binding occurs much more rapidly and you get what we call "crow-hopping" as the tire with the least traction releases the bound up energy, hops, and the process repeats over and over.
It's just the way the system works as these aren't true "All-Wheel Drive" systems. The compromise was Auto/A4WD mode where the front wheels aren't locked to the rear (so no binding occurs) but the transfer case is
ready to lock them quickly to send power forward if it detects the rear wheels slipping.
I suspect the "locked-up" feeling you experienced was actually just going into 4HI in conditions that don't let the wheels slip--but pardon me if I'm making some bad assumptions about your situation.