Thanks for the answers. So I guess it is now certain that Pat the Brat is not PD. No chance of discovering it is PD after all, right?
That's just my bad luck. Since I already translated quite a lot, here is a question. What are the chances that the next comics I choose to translate will also be found non-PD later? Please, do not take this as a complaint, I really appreciate your work here on DCM. I just want to make sure this bad luck will not happen to me again

BTW, do you think it's worth trying to get some sort of license on publishing the translated Pat the Brat free of charge on my site? Will any agent even bother to reply to such request from a little guy?