Out of town for 3 1/2 days and had a neighbor opening up the door to the run in the AM (not checking on birds) and allowing the girls to free range for a bit in the evening (not checking but aware of them coming out of run/coop) before closing up the coop at dark. Left Thursday afternoon, her initial symptom of slight lethargy was not noticed until Saturday afternoon, we arrived home 7pm Sunday. The caretaker reported that on Saturday evening he noticed our vivacious yet scrawny (4lbs compared to our biggest, a Buff who is 8lbs) 3 yr old, NHR was slow to come out to free range, she is usually the first one out the door. On Sunday afternoon, caretaker reported she was weak, lying on coop floor and didn't come out to free range at all. When we arrived home, went to check on girls found her on the coop floor, tail drooping, extremely weak. Immed. brought her inside our home thinking it had something to do with sudden cold snap??? Only dropped to 28ª F, not crazy cold. Inside she felt warm enough, would not eat or drink anything, no drooling just limply sat on my lap, barely holding her head up. Checked her vent which appeared patent, (have no idea how to proficiently check for egg binding or what most noticeable symptoms are). After examining her she had, for lack of a better word, 3-4 short, mini seizure-like episodes, lasting for about 5-10 seconds. Because everything happened so quickly, finding her to her death in a fifteen minute time frame we have no idea of the progression of symptoms prior to finding her. She poo-ed once in while on my lap wrapped in a towel, no blood, possibly some yolk like color and after the mini seizing-like episodes began what seemed like gasping, panting??? repeatedly opening her beak. Other: her abdomen was NOT distended, vent NOT swollen or inflamed, comb wattle normal color, no eye, nose or mouth discharge. OF NOTE :she kept her eyes closed most of the time in the brightly lit house, could not stand, extremely lethargic/weak. Historically we don't think she ever laid a solid egg (many times we would find a broken,soft shelled - as in shell was thin, rubbery membrane that left a wet gooey mess in nesting box) but b/c we had 9 (3 Australorps, 3 Buffs, 3 NHRs) we were never certain who was laying what. There is oyster shell in their layer feed, Egg peritonitis??? w/o abdominal distention, egg bond w/o bloody stool??? or runt that lived a lavish 3 yrs. P.S. In hindsight while caregiver could have given us a heads up, other than feeding, suppling fresh water he knows very little about chickens. He did not find her on floor of coop until 4-5pm Sunday, we were already on our way home, arriving 3 hours later. We do not live in an area with NO veterinary care for chickens AND would have had a terrible, worrisome ride home if he had notified us. Looking for closure but w/o an autopsy don't think we will get it. Our research of possible causes of death indicate that when symptoms are discovered it is usually too late. Of the 9, she was one of the favored b/c of her spunky personality. Thanks in advance for any expert advise, tips for prevention in the future. This is our second flock, 1st lasted less than a yr all but one killed by neighbors dog and hawk.