May be you have the other Foglet in your hand?
Only the options given by 4RM3D are the possibilities:
1) Either you have the other Foglet in hand. It doesn't spawn and summon, but rather summon the copy from deck.
2) It was locked.
3) It was banished (either by the bomb or by Regis:BloodLust)
[There is a remotest 4th possibility that you had only one Foglet in your deck]
[There is another remotest 5th possibility that the Foglet on board on which you are trying was itself summoned by the deathwish of the other Foglet]
So, if you can reproduce it fairly consistently, Take a screenshot before you are reproducing the issue and after it happens. The board, the deck and the graveyard. Since you can reproduce it in practice mode, it shouldn't take you any time.
Again, I/we am/are not insulting you. We just want to help you figure out the issue and for that we need your help.