Have you read it?
On the web, I found something that purports to be his final voyage, but there's one part where Tichy behaves...rather inappropriately, so I'm not certain whether it's genuine. (without going into details, it involves a secretary)
By final voyage, I mean the ostatnia podróż that Lem wrote in the nineties, not the old dwudziesta szósta i ostatnia story.