Get a quick screenshot. There's a lot of ways detail sprites can look wrong.
Edit: If you're using a custom detail sprites file, it's possible that your coordinates are wrong. You also might be using a custom detailsprites.vtf without knowing it, so check for that.
If the problem is that they're showing up in places that you feel they shouldn't, then you'll have to either rework the alpha on your displacement or make your own detail sprites file to read from.
Detail sprites are placed according to alpha levels. The levels are specified in the designated .vbsp file (default being detail.vbsp, located in the mod before).