事がなければ meaning in this sentence

Question

宛名も差出人の名前もない紫の封筒があるわあるわ、ざっと目算して三百通は下るまい。
呪、もしくは念が宿るのかもしれない。
何の意味もなく、それらが有象無象の雑多な願いにすぎなくて、そして、ここまで蒐集されてなお人目につく事がなければ、さぞ無念が生じるだろう。

According to my calculations there could not be less than 300 purple letters with no address and without the name of the sender.
Curses, or maybe they contain hope.
Without any meaning, those are people wishes and nothing more, moreover to be collected to this degree and the fact that they might not come to bee seen, I am sure there will be many regrets.

What does that bold sentence mean?

The fantraslation goes something like this:

Should they ever be brought to light they would produce many regrets.

ここまで蒐集されて=Be collected up to this degree
なお=In addition to that
人目につく=Come to light
事がなければ=This situation does not happen (conditional)
さぞ=I am sure
無念=regrets
が生じるだろう=Will probably arise

Edit: 人目につく=Be visible, Be under public view.

So

If they are not visible, it will bring regrets.

Still it is differend from the fantranslation.

Answer 1

Have you checked the links given by broccoli forest? Then think of this こと as occasion or chance.

• 人目に付くことがなければ ≒ if there is no chance to be seen ...

Here's my best translation attempt:

ここまで蒐集されてなお人目につく事がなければ、さぞ無念が生じるだろう。
Having been collected to this degree, yet having no chance to be seen, they (=the envelopes) are sure to hold a deep grudge.

So the author is thinking those mysterious unread letters are almost becoming like vengeful ghosts, because their innate desire as a letter has never been fulfilled.