Could Not Reproduce Persist Creature failed to return

[Zim031]

I attacked with an Obstinate Gargoyle in a Sealed League game and it was blocked, killed but did not return.
No counters of any kind where on my creature and it was not exiled either but rather just ended up in my graveyard.

https://flic.kr/p/2pZurXE

 

[Neo001992]

I couldn't get this to reproduce itself in solitaire testing, but that doesn't mean much when you have video of the cards not behaving as expected.

https://imgur.com/a/qRythM3

Event#269856255 Game#882616540