You may be right, but I'm not sure we can be certain from what we've been told. I've seen players do something like this on a few occasions; sometimes they have been trying to lead, sometimes not. I've seen a player who overheard "three diamonds" at the next table attempt to lead the ♦3 during the auction. He was making a lead by his own admission. I've also seen someone with dementia place the ♥4 on the table. He was trying to bid hearts, not make a lead. Since the card was not an honour card, I think we need to ask the player a bit more about what he thought he was doing when he placed it on the table. If he was putting it there as an attempt to contribute it to a trick, since it would be the first card in that trick I think it would have been a lead. If (as may well be the case) he was trying to make a bid but using the wrong card to do it, then I think it would not be a lead, and we are in L24A territory.