|At this point, I wouldn't worry too much about either issue. I used to think that my diapers had a slight urine smell when I took them out of the washer. It wasn't obvious: I had to bury my nose in them to smell it. And after they dried, they didn't smell anymore. My solution was to stop burying my nose in the diapers when they came out of the washer! All that to say that it may just be that your sense of smell is very sensitive, which I assume it would be in your situation. If it's only one diaper, it could be caused by the delay in washing it, but chances are that after another wash it will be just fine. Of course I'm talking about a slight urine smell here, not a strong ammonia smell or a urine smell that turns foul as soon as the baby pees (which usually indicates buildup). I would personally use the diaper - maybe not for nighttime, so your baby is not in it for too long if you're worried about it. If it comes out smelling again after the next wash, or if several of your diapers start smelling, then I would worry about buildup, but it seems like it would be really fast for this to happen.
As for stains, I really can't imagine there would be a way to tell without seeing the diapers, but again, I wouldn't personally worry about it. Stains are not dirty, they're just stains. They don't affect the performance of the diaper, only maybe their resale value if you're planning on doing that. Some people do use a bit of bleach once in a while, but bleach IS bad for the diapers. You can get away with using it once in a while, but if you can avoid it, I think it's better. I have only seen it recommended for people with really bad stink issues that wouldn't be solved any other way, or for persistent yeast infection issues. But it is bad for the fabric and for the environment. So if it's just for stains, I wouldn't risk it.
You can dry your diapers in the sun, it does wonders to remove stains. Personally, I find that my diapers get really stained in the summer (due to large blueberry consumption), but during the winter the stains mostly wash away. They don't bother me. I guess some people would find them gross, but I know the diapers are clean. Another thing some people do is dye their stained diapers to cover the stain. But in your case, since you don't see the stains anyway, I guess it would only be to appease your DH? I don't think it's worth the trouble!