Found a SanDisk micro SD Ultra 32GB and checked its content (and with that I took the risk of infecting the computer in some way but it's clean, I think). This card belonged to an Android phone from a young couple on holidays. I asked SanDisk if I could just send them the card and then they'd take care of returning it to the original owner but no dice there. Is Facebook the only solution? I really despise using Facebook but on the other hand I feel this couple would like to have their stuff back. If only there was a "If this card gets lost please send to" info on the card it would be super helpful but we never expect this to happen.