I would like to use an Adobe Stock illustration with an organizational logo for an event. It will not be registered as a trademark or used after the event.
This has been covered in the FAQ : Adobe Stock Help | Common Questions
Can I use an Adobe Stock image as part of my company logo or brand?
No. You need to have complete ownership of the image you use for your company logo, since logos are intended to be registered and protected to prevent other companies or organizations from using the same image. Because Adobe Stock only grants a right to use images and does not transfer the ownership, these images cannot be used in or as a logo.
Hope that answers your question.