I'm afraid you might be slightly confused.
1. What you highlighted was a series of text characters that are almost completely general, and not specific to pixiv( or any website) work filenames.
By definition, you can't expect people to know just by the file name on display that it's a work from pixiv unless it actually has the word "pixiv" somewhere in that file name.
Try searching the web for "87782660_p0" like I did, and try not to be surprised if the only result you get is this website thread, like I did.
2. I'm certain plenty of people have tried the image searches, knowing how to use them, and gotten nowhere because every single image search site led them to a dead end.
This is quite commonplace with pixiv exclusive images, because of how that website, just as many others do, restricts the viewing of adult works, as this clearly is, so that you have to be logged in to see it.
3. Have you ever tried direct linking to a pixiv work image file? You'll find the website does not allow it, causing you to see a forbidden 403 error page.
In other words, even if that had been a proper file name, it wouldn't work, because of that. I've tested it for myself and found the only way is to paste the URL of the work page for the file like so: https://www.pixiv.net/en/artworks/seriesofnumbers
Something to think about.