I'm pretty sure some of my recent upvotes on questions have been lost. I'm almost positive I upvoted this question when it was new, and I just discovered that I had no glowing arrow and could vote again. And I've noticed that the same is true for other recent questions in the (tag:mi-yodeya-series). (It may well be true for other questions also, but I don't necessarily remember which of those I've previously upvoted and which I haven't, whereas I'm pretty sure I've upvoted all recent mi-yodeya-series questions that I've answered, and there are quite a few such questions that I've discovered my vote discounted on.)
edit: I've discovered another: 11007. it's not in the mi-yodeya-series, I commented "+1", it looks the kind of question I would have upvoted, and it's not marked with my upvote.