I bought two little games today.
They are still in the list of the games I own and the installation links are active, so no harm done there.

But the purchase history first didn't acknowledge the deal was done (a link appeared in its entry, along the lines of "Finish the transaction/purchase"). And now that entry completely disappeared from the purchase history.

Not a huge inconvenience, though I'd prefer the purchase history to work...
Should I contact someone, or will it resolve itself? Thanks.

Open a support ticket. Don't assume the issue will resolve itself, or that the games won't disappear from your account.

Also make sure you keep your confirmation mails - just in case.

Thanks for the suggestions.
The e-mails.are safe and I've sent the request through the help page form.

Out of curiosity, how long does it take on average (or in your experience) to get a response, once you send the help request?

It didn't happen to be for a bundle, did it? I had recently been looking for a game in my order history but I had to look for the name of the bundle instead of the game.

No, it was two separate games.


EDIT: The issue has been finally solved by the help team.