Mutants and Cruel Dynomancer bug

I was playing my dinomancer deck

new dino

Class: Warlock

Format: Wild

2x (0) Raise Dead

2x (1) Kobold Librarian

2x (1) Mortal Coil

2x (2) Defile

2x (2) Expired Merchant

2x (3) Backfire

2x (3) Dark Skies

2x (3) Free Admission

2x (3) Luckysoul Hoarder

1x (3) Tamsin Roame

2x (4) Cascading Disaster

2x (4) Hysteria

2x (4) Lesser Amethyst Spellstone

1x (4) Spiritsinger Umbra

2x (4) The Dark Portal

2x (6) Cruel Dinomancer

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My opponent was playing quest murlocs.

A random Mutanus appeared in my hand on turn 7 after my opponent completed his quest but before he played the reward.
When my opponent played megafin, I cast hysteria on it and my dinomancer then randomly came back as mutanus after dying (but I never played the card or discarded it) and added a second Mutanus to my hand.
The next dynomancer I played met a similar fate after dying to toxin flurgl combo, it also came back as mutanus and added a third copy to my hand. I have a link to the hsreplay replay if you want it, I cant include it here.

Thanks preformatted text and block quotes still gave me the you cant post links error

Or simply put:
hsreplay.net/replay/yBXHWwmQrZCH2GMJeJTVSB

Turn 7: Your opponent played Fishflinger, which gave you Mutanus. Next turn, you played Expired Merchant, which discarded your Mutanus.

Missed the fishflinger, thanks

You did missplay on turn 14. I would have played Umbra and then Dinomancer to develop a board (even with the poisonous Flurgl), and saved Raise Dead in case you got Spellstone (which you drew next turn). Playing Raise Dead served no purpose, especially since you played it after Dinomancer, missing the corrupt on Hoarder. But that’s got nothing to do with your question.

Yeah, the random mutanus threw me. Was definitely a winnable match, was worried the poison would stop them coming back, like moonfang, as wasn’t sure of the interactions for the card or what I was seeing.