Some random dude pulls up to me, asks me trade me an item and then to give it back. He gives me around 12000 runes and then sends another trade request. Thing is, I can't give back his runes. It says : You can offer that item in X hours, X minutes, or when you have 7 QP. I inform him of my problem and ask if he'd like for me to simply drop them and for him to pick them up which he accepts. I drop them and he tells me he has to wait 1 minute to be able to see it. After 1 minute, the runes disappear so I assume he picked them up to which he tells me he didn't. I inform him that they've disappeared and he asks me to show him my inventory through trade. I tell him that i cannot and am still getting the same message. When I asked him why he gave them to me, he said something about an experiment to see if players were still nice or something. He then tells me goodbye and disappears. Is this some sort of scam ?