When your child requires discipline, it is often ineffective to simply use the same level of punishment for all their misdemeanors. Failure to clean their room vs. being disrespectful to your authority are on different scales, generally. If you simply send them to their room for everything, they won't learn that various actions have various consequences. The specific example I have in mind is when your child loses something important, such as their art class paintbrushes or soccer cleats. There are a few steps that should be taken in these cases, and a very motivating punishment as well.
1. The child should look for the missing item. Scour the house. Dig under their bed. You may help them search, but do not do all the work for them.
2. If the item is not found, make the child pay for it (or at least part.) Having to part with even a small amount of hard-earned money will burn the lesson into their minds. They will be extra careful with their possessions and take special care not to lose them again.
3. Oftentimes, the threat of having to pay themselves for the missing items increases the determination to find the lost thing ten-fold. Good luck! And you can, of course, always pray to St. Anthony, patron of lost causes.