"For you have died and your life is hidden with Christ in God."
When someone hides something, the intent is to keep it secure. Many people hide their money, jewelry, etc. for that very reason. However, when we hide something there's always a risk that what we're hiding will be discovered in spite of our efforts. In part this is because we lack omniscience, among other things. But what about Christ? Is it not safe to assume that Christ can keep us hidden? Why would we doubt that He could?
If it was possible to lose your salvation, (be "found") why would the Holy Spirit have chosen this language?
Sounds to me like Paul wants believers to understand that they are secure, period.