Gemini 3???
Funnily enough if you look at the transcript from Apollo 17 EVA2 at the point when this sample was collected there was the following exchange between Bob Parker, the Capcom, and Gene Cernan:
144:40:45 Parker: Okay. (Pause) And don't forget to put your little note in the long can there.
144:40:55 Cernan: Oh, I'll get the note in there. I'll get it in there. (Pause) Nobody will ever know! (Long Pause)
When a decade or more post the event Cernan and Schmitt reviewed the EVA records for the benefit of the Apollo Lunar Surface Journal they made the following observations
[Schmitt - "There was no note. Gene and Bob were just teasing the scientists, threatening to contaminate the sealed sample. This was a real-time 'put on' that Bob came up with; and Gene just fell in with the spirit of it instantaneously. I'm pretty sure it wasn't planned, although it could have been based on something that had come up in training."]
[Cernan - "I don't remember this, but I don't think there was any note. It was just a little bantering back and forth between Bob and I to make people wonder. I'd like to know if that can's ever been opened, because I think they were going to keep it sealed for some indeterminate length of time."]
[In a recent conversation, Bob recalled that this sample was going to be preserved in pristine condition until significantly better analytic techniques became available. During training, they had joked about putting in a note. The long can would be a time capsule and the note would be a surprise greeting from the past. Of course, an actual note would have contaminated the sample and would have spoiled the joke.]
https://www.hq.nasa.gov/alsj/a17/a17.html