What you were expecting to happen, and what actually happened:
I expected to get some more pets but I didn’t._
How often does this happen? When did it begin happening? Was this a once-off bug or has it been a consistent issue? Does it only happen after doing a particular game mode?
After rescuing Minfernus I collected the rewards but they didn’t show up in the troop menu as shown on the screenshots. When looking at the pet info it says I need 6 more to level up so I should have 9 but in the troop menu it says I only have 5.
Steps to make it happen again
No idea, I guess play pet rescue?
You don’t need to sacrifice 15 copies, you need to sacrifice 10 copies to get it from epic to legendary.
So you do have 5 as it says on the bottom of the second picture and you do need 6 more copies so you can sacrifice 10 and have 1 more at legend.
It is showing “Cost 10 (cards)” in the top middle of the second screenshot.
There have been similar issues with the players confusing the Troops Ascension so I’ve made a note of this for the team to potentially look into in the future and also updated the Pets Article with more information.
I also reworded your title in case it helps other players.
