Can a horse lie down and sleep while tied to a hi-tie?
I've only been to a few rides and so far haven't bought a pen or other device. I've tied to the trailer, and I've tied to a picket line when trees were available, and to a permanent tie-pole. My horse (Peruvian) was able to lie down tied to the picket line and even the tie-pole. I'm planning on using an electric pen in the future, my horse has a great respect for anything that looks like electric string. My junior rider's Arabian paced when on the picket line and he seems to do best just tied to the trailer.
As for loose horses, we've had our fair share of loosy gooseys. At our first 50, the Arabian got loose during the night but only went as far as our neighbor who found him and tied him back up. Culprit was wrong type of lead rope. Next 50 mile ride, when my horse was on the tie-pole and her horse was at the trailer we had an interesting time. First nite nothing happened as I recall. Second nite we came back from the ride awards and my Peruvian was standing 10 feet away from the tie-pole staring at it. He was just standing there in the gravel road not moving. We think he got his leg caught and he pulled loose, the rope slipped off the tie ring, and he was contemplating that scary tie-pole. He was still attached to the lead rope. Didn't go anywhere! For a few hours he was wary of the tie-pole but eventually accepted it again and laid down at nite. Then in the morning I awoke to some noise. The Arabian was loose again and was playing with a stepping stool outside my tent. The Peruvian was just watching him. I think we have good horses and obviously a houdini who plays w/ his rope and another who doesn't care to run about and leave his buddy.
As for everyone else, I've seen loose horses running rampantly at nearly every ride. Luckily ours seem to be "yard trained" and very mellow.