Person who suffers from unrequited love

I'm looking for a noun that describes a person A, who loves person B, but person B doesn't reciprocate. Person A suffers because he or she can't have person B and is not interested in relationships with others.

The shorter the word, the better (ideally -- single word).

Sample use in a sentence:

It poured as if it rained tears of all people who suffered from unrequited love.

I need a substitute for people who suffered from unrequited love.

Collins gives the meaning :

miserable because of unrequited love or unhappiness in love

for the word 'lovelorn'.

Also, Cambridge

sad because the person you love does not love you

But note that both sources are defining the emotion (miserable and sad) of the recipient (or rather non-recipient). They are not defining the state of being in a situation of unrequited love itself.

However I think that the noun, the lovelorn, answers the OP as the question was about a 'person who suffers'.

Heartbroken

A word that can be used for this situation is heartbreak, defined as

very great sadness and emotional suffering, especially after the end of a love affair or close relationship.

The corresponding adjective, heartbroken, fits your sample sentence perfectly, although the meaning is not restricted to unrequited love:

It poured as if it rained tears of all the heartbroken.

Lovesick

If you want a word that is less generalized, you should consider lovesick, defined as being

sad because the person you love does not love you.

In that case, your sample sentence would be as follows:

It poured as if it rained tears of all the lovesick.

If you're striving for a more modern / comedic tone, you could say "all the friendzoned people".

limerent.

It's based on limerence, a word coined by a psychologist to describe "an involuntary cognitive and emotional state in which a person feels an intense romantic desire for another person (the limerent object)."

However, the word's usage is 1) confusing and 2) unfamiliar to most people.

It can be used as an adjective (e.g. "limerent object"), but it can also be used as a noun...

The long fantasies form bridges between the limerent's ordinary life and that intensely desired ecstatic moment.

Since the word is so unfamiliar, you may need to describe it before using it, or define it in a footnote.

Limerence