I think another reason was how I held him, which caused him to stretch his head forward (effectively pressing his ears backwards). I also notice that hamsters, when running really fast, tend to press their ears down (maybe to decrease wind resistance? I call it "the sports car").
Never the less, I thank you for your concern. If you are interested, please do check out my other hamster pics/comics, and I hope that will convince you that my hamsters are well treated