Most hotels do have a lost and found process of some sort - but even then things get miss placed. When I worked front desk the head house keeper would bring us the found stuff everyday in a bag with the room number on it, but if someone called about something we didn't have at the desk I would sometimes find it in the oddest places. On shelfs in the laundry, or supply rooms, on their lunch table, or under the folding table... I don't think there was ever any malicious intent, but we are all human, and good intentions aside things get misplaced and overlooked (remote control in fridge syndrome). You may try calling back one more time just to see if it's popped up somewhere- or possibly just been tossed in a drawer with the rest of the random cords.