Oh my ... that's one of the reasons why I call my speckled sussex a space cadet, she's a loner too. I always thought it was because she spent the first 2 weeks of her life in her own little brooder (she had a broken leg) and didn't become socially adept. She could care less what the other 40ish chickens are doing in a pack and would be in her own little spot, digging, not a care in the world.
If you can't tell, she's my favorite chicken, hands down.
One night in the summer I couldn't find her. I had let them out to free range while I did chores. I had seen her about 5 minutes before I went to lock the coop up, digging in the yard. But I go in and count, and I'm missing a chicken. I always look for her first and of course she wasn't there. So I go outside, and call her... nothing. I go back inside, look again, this time good, in the nesting boxes, etc... no Hoppy. I go back outside and call her, nothing. I walk around the coop and look under it. Nothing. I look in the compost bin (she's sometimes in there digging away, oblivious to the world)... nothing. I walk around the house, nothing. At this point I'm starting to become seriously worried that she got eaten by a fox quickly, and am almost in panic mode. I go back into the garage (I leave the doors open in summer) to get a better flashlight and there she is at the top of the garage stairs, at the house door - looking at me like, I sleep in here, ok?
Oh and she begs for treats... *they're molting here... they look terrible*