Hello David,
Hering's Guiding Symptoms are principally a collection of CURED symptoms.
Some of the listed symptoms are those that were originally produced in provings then were subsequently found to be clinically curative.
In other instances there are symptoms that were not produced in the original provings but were repeatedly found to lie within the curative sphere of the remedy in different patients. Hering believed that these cured symptoms with further investigation and confirmation were beneficial to our MM knowledge base. As Hering said himself, obviously a proven and clinically verified symptom is the best guide as a characteristic indication.

In the Preface to his Guiding Symptoms, you will see a list of symbols, that when read in context, give a value to the particular therapeutic indication.

Hering: "To facilitate the study of the relative value of symptoms, four marks of distinction have been adopted, |, ||, ¤, ¤¤, which correspond to the four degrees in Boenninghausen's Repertory.
| is the lowest, and designates an occasionally confirmed symptom. It is omitted in most cases, and is sometimes used to mark a difference of value in the same line.
|| Symptoms more frequently confirmed.
¤ Symptoms verified by cures.
¤¤ Symptoms repeatedly verified.
"A pointed finger" indicates an approved characteristic, but is seldom used, by reason of our not wishing to appear authoritative. It is to be hoped that the combined experience of many practitioners, solicited from all sides, will enable us in a future edition to designate many more symptoms with this mark.
ð The Greek letter "theta" stands between the cured symptom and the pathological condition, or the physiological general state, f. i., pregnancy or climacteric years. This by no means excludes the characteristic nature of the symptom in other forms of disease.
{ Such observations from the Old School or the News as are worthy of our consideration.
t. Toxicological.
r. Right. l. Left.
< Increase, or aggravation; worse.
> Decrease, or amelioration; better.
p The Greek "pi" stands before symptoms observed only on the sick."

In the MM section of Phosphorus, this particular cured symptom is preceded by two ¤¤ which according to Hering signifies that it has been repeatedly verified as a cured symptom.

- ¤¤ Thirst : with desire for very cold drinks; for refreshing drinks, amel thereby until they become warm, when they are vomited; excessive; unquenchable.

Kent wrote: "The pains in the stomach are ameliorated by ice-cold things for a moment; spasmodic contractions of the stomach; haemorrhage from the stomach; vomiting of great quantities of clotted blood; long-standing dyspepsia; much flatulence; regurgitation of food; distended stomach and abdomen; ulceration of the stomach."

In Chronic Diseases we read:
Symptom no. 745: With the most dreadful tortures, he attempted to vomit but could not, only the drinking of cold water alleviated his pains.

Symptom no. 809: Severe burning in the stomach, with violent thirst, anguish, convulsions of the face, violent shuddering, cold limbs, clear, watery eyes, pale lips, weak pulse, decrease of strength and - death.

Poor guy!

Clark, Borland, HC Allen are some other authors that have subsequently afforded the symptom a "keynote" quality but it does pay to put it in context.

Chris.