Lost a troop card

Hello, my husband and I are still fairly new and still in the process of learning about each part of the game and meanings to those parts, My husband was trying to figure out the desenchantment and had 12 cards of LOYALTY, so he desenchanted all but the two that troop card needed and now that card is no longer within his troop deck. why is that? how can he regain that card back?
Why when you choose to take a trait and or asension with one card do you lose the upgrade opportunity with the other cards(that also had traits and or asensions available).

I can’t help you with the missing troops; if you truly believe these were lost and not disenchanted to a count of zero (yes, this is unfortunately possible), you will want to open a support ticket to request recompense.

As for traits, these cost a resource called “traitstones” to unlock. If you unlock a trait on one troop and doing so causes your traitstone total to drop below the amount needed to trait another, you won’t be able to unlock the second troop’s traits. You will need to be strategic about which traits matter to you most. Similarly, leveling a troop requires souls, and for lower level players this resource can limit your ability to level everything. Ascension simply requires duplicate cards; ascending one troop should not preclude you from ascending another.

Welcome to Gems of War and the community!