I think this is a bug. My steel type Scizor was poisoned by Seadra. The only way for a steel type to be poisoned is through the ability corrosion which Seadra does not have. 

@Vatevuoktliek

 

There's the possibility that the trainer used Soak on you with another Water Type such as Golduck and then you made physical contact with Seadra, which can have the ability Poison Point. Since you became a Water Type after being Soaked, you were poisoned.

I forgot to put battle logs, but soak was not used on my pokemon. I used bullet punch on seadra which triggered poison point, but that should've been impossible on a steel type like scizor.

Edited August 27, 20232 yr by Vatevuoktliek

Without Battle Logs there's not much that can be checked sadly.

5 minutes ago, Bhimoso said:

Without Battle Logs there's not much that can be checked sadly.

Yeah, hopefully I'm wrong and it's not a bug.