I played Tess Greymane where I had earlier played ancestral guardian (paladin minion), but her battlecry did not re-summon it. She did however re-summon a menacing nimbus earlier in the game. I double-checked by playing Tess twice in this game and both times the Ancestral Guardian was not resummoned even though the menacing nimbuses were. The game log is in the URL below (replace [dot] with ‘.’). This seems like a bug.
Relevant cards: Tess Greymane, Ancestral Guardian
Cards played from other classes this game: desperate measures (x2), arcane intellect, moonfire, ancestral guardian, menacing nimbus (x1 for the first Tess, x2 for the second Tess).
Game Type: Standard, Rank 12
Platform: PC
Replay URL:
www[dot]zerotoheroes[dot]com/r/hearthstone/5d845c427687de000182deb0/tess-greymane-bug-not-resummoning-ancestral-guardian