A website where intellectual property control can be done?

Hello.

My stick figure illustration (AI generated) below was rejected due to "Refusal of Intellectual Property". This happens from time to time.

Of course, I send such submissions without knowing the situation in question. But I don't know what is protected by intellectual property and what is not. (I also read Adobe's list of known copyrighted works, but I didn't see any reference to stick figures, if I remember correctly)

I wonder if there is a reliable website where I can check the intellectual property of my work before uploading it to Adobe Stock?

Thank you.