Suspicious Pirate doesn't work in Arena

I just finished playing two rounds of arena, and I played the card suspicious pirate. Both times, the card mechanic did not work.

Sucks 'cause I have two in an arena (paid) deck that I can’t edit.

People are going to tell you that you were playing a class that doesn’t have available weapons to discover
Which is inconsistent with how other cards still allow you to discover when your class has no available card

However, the dual class arena does not make you actually dual class. If you pick for example druid-warrior, you will be able to draft from both classes, but once in game you will only be a druid (the first class you picked and have the portait of)

Yes, because that is the best answer we have.

No, the best answer we have is “we don’t know which one of the behaviors is the correct one”
“I don’t know” is a valid answer

You can’t say “you can’t discover cards that don’t exist in your class” when counter examples have been existing for years, the oldest being 7 years old, and while other counter examples are currently existing in modern standard

However we can guess.
This “bug” only started being reported recently, (I admit mostly thanks to the dual-class-not-so-dual arena) which means something has changed, either on how cards have been implemented recently, or on how the context has changed throughout the years.

My personnal guess is that

  1. you should be able to discover cards from the original class of the card when they don’t exist in your current class, since it has been the rule for years
  2. Azsharan Scroll is bugged on its own because of how it has been implemented with its 3 discovery pools
  3. The other cards not allowing you to discover from their own class behave like that because the class actually had eligible cards in the past, meaning that that pool exists for the class

Examples for the third point :
Mage has never had fel spells in history. Mage does not have a fel spell pool. If you play Taste of Chaos in mage, you will be able to discover a demon hunter fel spell.
Druid has had weapons in the past. Druid has a weapon pool, that is currently empty in standard. If you play Runes of Darkness in druid, you will discover nothing.

Obviously, I’m eager to learn about counter examples of such theory to find what makes these behaviors consistent in their own ways

That might be because Taste of Chaos discovers a specific subtype of card. Not just a spell, but a Fel spell.

Suspicious Pirate, on the other hand, discovers a general type of card: a weapon.

The wording is different, so it’t not unreasonable to think the underlying game rule might be different also.