An Azure NoSQL database service for app development.
@Tyler Suard I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others ", I'll repost your solution in case you'd like to "Accept " the answer.
Issue: You have created an index for MongoDB vCore, but when you query the database using a vector, you are getting the error "Similarity index was not found for a vector similarity search query."
Solution: As you mentioned you have set the wrong database and collection and by correcting your issue got resolved.
If you have any other questions or are still running into more issues, please let me know.
Please remember to "Accept Answer" so that others in the community facing similar issues can easily find the solution.
Regards
Geetha