I would go with missed powder charge as well. Primers (depending on which one you used) are definitely powerful enough to move the bullet into the bore.
One caution is when loading something like Titegroup in a case like a 38 or 357M, it is just as easy to double as miss, likely good to review you proceedure and see where you can tighten it up. Double is always worse than no powder.
When asked what qualities he most valued in his generals, Napoleon said, "give me lucky ones."