Please check the following sentences.
1. At first, I looked for a covert to hide myself.
2. Soon I found a secret closet which was hard to be noticed to conceal.
3. After a long time, no one detected where I hid.
4. I felt pleased that I would be the winner of the game, but not showed it.
1. I have never heard "covert" used as a noun. It's in the dictionary, but not common. I would say I looked for a place or a way to hide myself.
2. ... which was hard to notice.
4. ... but didn't show it.