I'm really just asking out of desperation, as I don't think there's a good answer to it, but who knows? I take it there is no comfortable way to search our Private Messages here on GOG? I've talked to nearly 150 GOG members via PM and somewhere hidden among these conversations is a piece of information I'm looking for. Is there really no other option than to expand the whole list of contacts click by click and then click on and search each conversation individually? :/

There is no other way.

You could ask the person you talked to, if you know who he is .

If I remembered who the person in question was, it would be easy to find that relevant piece of information. ;)

It can be easier if you remember which user sent you this info (or to whom you sent it). In such a case you only need to find any of his/her post and click orange "PM" button. You'll be taken to your conversation with that person immediately, without browsing through the list.

But I'm afraid you don't know this user, do you? In such a case manual browsing seems to be the only option. Sad.
EDIT: you've already answered this question ;)

That sucks. I really don't envy members like nmillar who has to manage the Secret Santa gifting each year under these conditions ...

Anyway, the good news is that it seems my memory isn't as unreliable as GOG's search functions; I scanned the PM list once again, got a sudden inspiration and found what I was looking for! :)

Since I have to mark one answer as the solution in order to close the thread, I'm going with Licurg's suggestion, because sadly that would have been my last resort if my intuition hadn't spared me this step. Thanks for all the replies!

Yay !

Damn, you found it. I was considering doing a PM Leroux to enter giveaway.

You mean, to make the search game even more challenging for me? :D