The game 13 used to be on this website, but it's been gone for years. Then, it was just recently added again, and like any reasonable person, I decided that I'd buy it as soon as it was on sale (because who pays full price for anything when they regularly put everything 40-90% off?). Anyway, after about a week it seems to have disappeared from the website again! What gives? If I knew that was going to happen that I'd have paid full price!

https://www.gog.com/game/xiii

I'm guessing you forgot it was written in Roman numerals and have been searching for "13" this whole time?

Yes, but I tried "13" and "Thirteen", and neither worked. This is quite a relief. Thank you!

GOG should tag certain games with invisible aliases, like '13' and 'Thirteen' in this case.

<tests some other games>

Hey, they seem to have done that or something similar to several games but I still quickly found one add-on, Alien Crossfire, not searchable by its title. At least Eye of the Beholder and X3:Terran Conflict can be found by their names now unlike before.

@GOG: Someone may pm me to ask for help identifying some more needed tags. Tell me where to send them and I will or better yet, make a thread where anyone may post them and then you read and take action upon the list.