I bought Police Quest 2 as part of a series way back.
But now PQ2 is gone from GOG alltogether.

Whats up?

It's still available as part of the Police Quest Collection that you can currently purchase for $14.98

https://www.gog.com/game/police_quest_1_2_3_4

I own the PQ Collection since several years...Why isn't it in my Games list?

I bought the POLICE QUEST COLLECTION way back, and I did have access to PQ2. For some reason I do not have access to PQ2 anymore. (unlike PQ1, PQ3 and PQ4).

I mean look at my purchase history:
Whenever has the Police Quest Series ever been sold seperatly?
I have PQ1, 3 and 4.
When has these games ever been sold seperetly at GoG?

Ok, for whatever reason PQ2 is back in my Game Library again.
I had to download it manually from the GOG website and install it for the game to show up in the GOG Galaxy library again.

For a while, they stopped selling the Sierra games as collections and sold them separately. There were posts in several forums wondering why they changed it. Then they went back to selling them as a complete collection again. If you bought the Collection and it doesn't have PQ2 in it, then you should report it to GOG