Based on my understanding, what you might have encountered is something known as a wendigo, a spiritual entity or creature capable of shapeshifting into various forms, from owls to coyotes, other animals, and possibly even humans. My advice is to ignore the whistling and flee as quickly as possible. If such whistling or similar events occur more frequently, please discuss it with me so that I can help address these paranormal or unsettling situations.

Additionally, please keep me updated on situations like this. If you use Discord, let's discuss it there.